Teach Yourself Electricity and Electronics Third Edition Book

Teach Yourself Electricity and Electronics Third Edition Book
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Teach Yourself Electricity and Electronics Third Edition Book

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    Teach YourselfElectricity andElectronics

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    Teach YourselfElectricity andElectronicsThird EditionStan GibiliscoMcGraw-HillNew YorkChicagoSan FranciscoLisbonLondonMadridMexico CityMilanNew DelhiSan JuanSeoulSingaporeSydneyToronto

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    Copyright  2002, 1997, 1993 by The McGraw-Hill Comp anies, Inc. All rights reserved. Manufactured in the United States of America. Except as permitted under the United States Copyright Act of 1976, no part of this publication ma y be reproduced or distributed in any form or by any m eans, or...

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    To Tony, Tim, and Samuelfrom Uncle Stanv

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    ContentsPreface xixPart 1Direct current1 Basic physical concepts 3Atoms3Protons, neutrons, and the atomic number4Isotopes and atomic weights4Electrons5Ions5Compounds9Molecules10Conductors11Insulators11Resistors13Semiconductors14Current15Static electricity15Electromotive force16Nonelectrical energ...

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    Power and the watt29Energy and the watt hour31Other energy units33ac Waves and the hertz34Rectification and fluctuating direct current35Safety considerations in electrical work37Magnetism38Magnetic units39Quiz403 Measuring devices 44Electromagnetic deflection44Electrostatic deflection46Thermal he...

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    Voltage across parallel resistances85Currents through parallel resistances86Power distribution in series circuits88Power distribution in parallel circuits88Kirchhoff’s first law89Kirchhoff’s second law91Voltage divider networks92Quiz956 Resistors 99Purpose of the resistor99The carbon-composit...

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    Magnetic field strength139Permeability142Retentivity142Permanent magnets143The solenoid144The dc motor145Magnetic data storage146Quiz149Test: Part 1 153Part 2 Alternating current9 Alternating current basics 165Definition of alternating current165Period and frequency165The sine wave167The square w...

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    Unwanted inductances195Quiz19511 Capacitance 199The property of capacitance199Practical capacitors201The unit of capacitance201Capacitors in series202Capacitors in parallel203Dielectric materials204Paper capacitors204Mica capacitors205Ceramic capacitors205Plastic-film capacitors206Electrolytic ca...

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    14 Capacitive reactance 247Capacitors and direct current247Capacitors and alternating current248Reactance and frequency249Points in the RC plane251Vectors in the RC plane253Current leads voltage254How much lead?256Quiz25915 Impedance and admittance 264Imaginary numbers264Complex numbers265The com...

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    Power transmission315Series resonance318Parallel resonance319Calculating resonant frequency319Resonant devices321Quiz32318 Transformers and impedance matching 327Principle of the transformer327Turns ratio328Transformer cores329Transformer geometry330The autotransformer333Power transformers334Audi...

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    Frequency control376Oscillation and amplification377Energy emission377Photosensitive diodes378Quiz38021 Power supplies 383Parts of a power supply383The power transformer384The diode385The half-wave rectifier386The full-wave, center-tap rectifier387The bridge rectifier387The voltage doubler389The ...

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    Depletion mode versus enhancement mode425Common-source circuit425Common-gate circuit426Common-drain circuit427A note about notation429Quiz42924 Amplifiers 433The decibel433Basic bipolar amplifier circuit437Basic FET amplifier circuit438The class-A amplifier439The class-AB amplifier440The class-B ...

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    Frequency and phase modulation482Pulse modulation485Analog-to-digital conversion487Image transmission487The electromagnetic field490Transmission media493Quiz49527 Data reception 499Radio wave propagation499Receiver specifications502Definition of detection504Detection of AM signals504Detection of ...

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    Radio-frquency power amplifiers544Cathode-ray tubes546Video camera tubes547Traveling-wave tubes549Quiz55130 Basic digital principles 555Numbering systems555Logic signals557Basic logic operations559Symbols for logic gates561Complex logic operators561Working with truth tables562Boolean algebra564Th...

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    33 Computers and the Internet 624The microprocessor and CPU624Bytes, kilobytes, megabytes, and gigabytes626The hard drive626Other forms of mass storage628Random-access memory629The display631The printer633The modem635The Internet636Quiz64034 Robotics and artificial intelligence 644Asimov’s thre...

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    PrefaceThis book is for people who want to learn basic electricity, electronics, and com-munications concepts without taking a formal course. It can also serve as a class-room text. This third edition contains new material covering acoustics, audio,high-fidelity, robotics, and artificial intellig...

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    three times. When you have gotten a score that makes you happy, you can check tosee where your knowledge is strong and where it can use some bolstering.It is not necessary to have a mathematical or scientific background to use thisdo-it-yourself course. Junior-high-school algebra, geometry, and p...

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    1PARTDirect Current

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    1CHAPTERBasic physical conceptsIT IS IMPORTANT TO UNDERSTAND SOME SIMPLE, GENERAL PHYSICS PRINCIPLESin order to have a full grasp of electricity and electronics. It is not necessary to knowhigh-level mathematics.In science, you can talk about qualitative things or about quantitative things, the...

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    Each element has its own unique type of particle, known as its atom. Atoms of differ-ent elements are always different.The slightest change in an atom can make a tremendous difference in its behavior.You can live by breathing pure oxygen, but you can’t live off of pure nitrogen. Oxygenwill caus...

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    nucleus results in a difference in the weight, and also a difference in the density, of theelement. Thus, hydrogen containing a neutron or two in the nucleus, along with the pro-ton, is called heavy hydrogen.The atomic weight of an element is approximately equal to the sum of the num-ber of proto...

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    6 Basic physical conceptsTable 1-1. Atomic numbers and weights.Element nameAbbreviationAtomic numberAtomic weight*ActiniumAc89227AluminumAl1327Americium**Am95243AntimonySb51121ArgonAr1840ArsenicAs3375AstatineAt85210BariumBa56138Berkelium**Bk97247BerylliumBe49BismuthBi83209BoronB511BromineBr3579Ca...

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    Ions7Table 1-1. ContinuedElement nameAbbreviationAtomic numberAtomic weight*LeadPb82208LithiumLi37LutetiumLu71175MagnesiumMg1224ManganeseMn2555Mendelevium**Md101256MercuryHg80202MolybdenumMo4298NeodymiumNd60142NeonNe1020Neptunium**Np93237NickelNi2858NiobiumNb4193NitrogenN714Nobelium**No102254Osmi...

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    from an atom, leaving only the nucleus. However it would still represent the same element as it would if it had all its electrons.A charged atom is called an ion. When a substance contains many ions, the mater-ial is said to be ionized.8 Basic physical conceptsTable 1-1. ContinuedElement nameAbbr...

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    A good example of an ionized substance is the atmosphere of the earth at highaltitudes. The ultraviolet radiation from the sun, as well as high-speed subatomic par-ticles from space, result in the gases’ atoms being stripped of electrons. The ionizedgases tend to be found in layers at certain a...

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    A compound is different than a simple mixture of elements. If hydrogen and oxy-gen are mixed, the result is a colorless, odorless gas, just like either element is a gasseparately. A spark, however, will cause the molecules to join together; this will liber-ate energy in the form of light and heat...

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    Sometimes oxygen atoms are by themselves; then we denote the molecule simply as O.Sometimes there are three atoms of oxygen grouped together. This is the gas calledozone, that has received much attention lately in environmental news. It is written O3.All matter, whether it is solid, liquid, or ga...

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    12 Basic physical concepts1-4At A, simplified renditionof molecules in a solid; atB, in a liquid; at C, in agas. The molecules don’tshrink in the gas. Theyare shown smallerbecause of the muchlarger spaces betweenthem.

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    Electrical insulators can be forced to carry current. Ionization can take place; whenelectrons are stripped away from their atoms, they have no choice but to move along.Sometimes an insulating material gets charred, or melts down, or gets perforated by aspark. Then its insulating properties are l...

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    Electrical resistance is measured in units called ohms. The higher the value inohms, the greater the resistance, and the more difficult it becomes for current to flow.For wires, the resistance is sometimes specified in terms of ohms per foot or ohms perkilometer. In an electrical system, it is us...

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    When most of the charge carriers are electrons, the semiconductor is calledN-type, because electrons are negatively charged. When most of the charge carriers areholes, the semiconducting material is known as P-type because holes have a positiveelectric charge. But P-type material does pass some e...

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    electricity. It’s called “static” because it doesn’t go anywhere. You don’t feel this until youtouch some metallic object that is connected to earth ground or to some large fixture;but then there is a discharge, accompanied by a spark that might well startle you. It isthe current, durin...

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    tive polarity (shortage of electrons) in one place and negative polarity (excess of elec-trons) in another place, a powerful electromotive force exists. It is often abbreviatedEMF. This force is measured in units called volts.Ordinary household electricity has an effective voltage of between 110 ...

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    Law. If the EMF is doubled, the current is doubled. If the resistance is doubled, the cur-rent is cut in half. This important law of electrical circuit behavior is covered in detail alittle later in this book.It is possible to have an EMF without having any current. This is the case just before a...

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    generator works. Generators can also work backwards. Then you have a motor thatchanges electricity into useful mechanical energy.A magnetic field contains energy of a unique kind. The science of magnetism isclosely related to electricity. Magnetic phenomena are of great significance in electron-i...

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    4. An ion:A. Is electrically neutral.B. Has positive electric charge.C. Has negative electric charge.D. Might have either a positive or negative charge.5. An isotope:A. Is electrically neutral.B. Has positive electric charge.C. Has negative electric charge.D. Might have either a positive or negat...

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    11. Movement of holes in a semiconductor:A. Is like a flow of electrons in the same direction.B. Is possible only if the current is high enough.C. Results in a certain amount of electric current.D. Causes the material to stop conducting.12. If a material has low resistance:A. It is a good conduct...

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    18. In some batteries, chemical energy can be replenished by:A. Connecting it to a light bulb.B. Charging it.C. Discharging it.D. No means known; when a battery is dead, you have to throw it away.19. A changing magnetic field: A. Produces an electric current in an insulator. B. Magnetizes the ear...

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    2CHAPTERElectrical unitsTHIS CHAPTER EXPLAINS SOME MORE ABOUT UNITS THAT QUANTIFY THE behavior of direct-current circuits. Many of these rules apply to utility alternating-cur-rent circuits also. Utility current is, in many respects, just like direct current becausethe frequency of alternation is...

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    often 12 V to 14 V. In household utility wiring, it is a low-frequency alternating currentof about 117 V for electric lights and most appliances, and 234 V for a washing machine,dryer, oven, or stove. In television sets, transformers convert 117 V to around 450 V forthe operation of the picture t...

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    In household electric circuits, the charge difference will essentially never equalize,unless there’s a power failure. Of course, if you short-circuit an outlet (don’t!), the fuseor breaker will blow or trip, and the charge difference will immediately drop to zero. Butif you put a 100-watt bul...

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    The ampereCurrent is a measure of the rate at which charge carriers flow. The standard unit is theampere. This represents one coulomb (6,240,000,000,000,000,000) of charge carriersper second past a given point.An ampere is a comparatively large amount of current. The abbreviation is A. Often,curr...

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    deliver an unlimited number of charge carriers, there will be a current of 1A. If the re-sistance is doubled, the current is cut in half. If the resistance is cut in half, the currentdoubles. Therefore, the current flow, for a constant voltage, is inversely proportionalto the resistance. Figu...

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    Resistance has another property in an electric circuit. If there is a current flowingthrough a resistive material, there will always be a potential difference across the resis-tive object. This is shown in Fig. 2-4. The larger the current through the resistor, thegreater the EMF across the resist...

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    about the conductance of a material, rather than about its resistance. The standardunit of conductance is the siemens, abbreviated S. When a component has a conduc-tance of 1 S, its resistance is 1 ohm. If the resistance is doubled, the conductance is cutin half, and vice-versa. Therefore, conduc...

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    Look again at the diagram of Fig. 2-4. There is a certain voltage across the resistor,not specifically given in the diagram. There’s also a current flowing through the resis-tance, not quantified in the diagram, either. Suppose we call the voltage E and the cur-rent I, in volts and amperes, res...

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    You will often hear about milliwatts (mW), microwatts (µW), kilowatts (kW)and megawatts (MW). You should, by now, be able to tell from the prefixes what theseunits represent. But in case you haven’t gotten the idea yet, you can refer to Table 2- 2.This table gives the most commonly used prefix...

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    Figure 2-6 illustrates two hypothetical devices that burn up 1 Wh of energy. DeviceA uses its power at a constant rate of 60 watts, so it consumes 1 Wh in a minute. Thepower consumption rate of device B varies, starting at zero and ending up at quite a lotmore than 60 W. How do you know that this...

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    Other energy unitsAs said before, physicists prefer to use the joule, or watt second, as their energy unit.This is the standard unit for scientific purposes.Another unit is the erg, equivalent to one ten-millionth (0.0000001) of a joule. Thisis said to be roughly the amount of energy needed by a ...

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    Physicists also use, in addition to the joule, a unit of energy called the electron volt(eV). This is an extremely tiny unit of energy, equal to just 0.00000000000000000016joule (there are 18 zeroes after the decimal point and before the 1). The physicists write1.6× 10–19 to represent this. It...

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    maximum, or peak, voltage. In fact, for the common waveshape shown in Fig. 2-8, theeffective value is 0.707 times the peak value. Conversely, the peak value is 1.414 timesthe effective value.Rectification and fluctuating direct current352-8One cycle of utility alternating current. The peak voltag...

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    The peak and effective values are the same for pure dc. But sometimes the value of dcvoltage fluctuates rapidly with time, in a manner similar to the changes in an ac wave.This might happen if the waveform in Fig. 2-8 is rectified.36 Electrical units2-9A representation of pure dc.Rectification is...

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    Using household ac as an example, the peak value is generally about 165 V; the ef-fective value is 117 V. If full-wave rectification is used (Fig.2-10B), the effective value isstill 117 V. If half-wave rectification is used, as in Fig. 2-10A, the effective value is about58.5 V.Safety considerati...

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    Household voltage, normally about 117 V but sometimes twice that, or about 234 V,is more than sufficient to kill you if it appears across your chest cavity. Certain devices,such as automotive spark coils, can produce lethal currents even from the low voltage(12 V to 14 V) in a car battery.Consult...

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    magnetized. Such substances are called ferromagnetic. A core of this kind cannot actually increase the total quantity of magnetism in and around a coil, but it will causethe lines of flux to be much closer together inside the material. This is the principle bywhich an electromagnet works. It also...

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    In general, the greater the electric current through a wire, the greater the flux den-sity near the wire. A coiled wire will produce a greater flux density than a single, straightwire. And, the more turns in the coil, the stronger the magnetic field will be.Sometimes, magnetic field strength is s...

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    B. 0.5 Ω.C. 0.05 Ω.D. 0.02 Ω.6. A resistor has a value of 300 ohms. Its conductance is:A. 3.33 millisiemens.B. 33.3 millisiemens.C. 333 microsiemens.D. 0.333 siemens.7. A mile of wire has a conductance of 0.6 siemens. Then three miles of the samewire has a conductance of:A. 1.8 siemens.B. 1...

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    C. The foot pound. D. The kilowatt hour.12. The frequency of common household ac in the U.S. is:A. 60 Hz.B. 120 Hz.C. 50 Hz.D. 100 Hz.13. Half-wave rectification means that:A. Half of the ac wave is inverted.B. Half of the ac wave is chopped off.C. The whole wave is inverted.D. The effective valu...

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    C. The gauss.D. The gauss-turn.19. A ferromagnetic material:A. Concentrates magnetic flux lines within itself.B. Increases the total magnetomotive force around a current-carrying wire.C. Causes an increase in the current in a wire.D. Increases the number of ampere-turns in a wire.20. A coil has 5...

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    3CHAPTERMeasuring devicesNOW THAT YOU’RE FAMILIAR WITH THE PRIMARY UNITS COMMON IN ELECTRIC-ITYand electronics, let’s look at the instruments that are employed to measure thesequantities.Many measuring devices work because electric and magnetic fields produce forcesproportional to the intensi...

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    likely, when this effect was first observed, the scientist tried different arrangements tosee how much the compass needle could be displaced, and how small a current couldbe detected. An attempt was made to obtain the greatest possible current-detectingsensitivity. Wrapping the wire in a coil aro...

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    Electrostatic deflectionElectric fields produce forces, just asdo magnetic fields. You have probably noticed thiswhen your hair feels like it’s standing on end in very dry or cold weather. You’ve proba-bly heard that people’s hair really does stand straight out just before a lightning bolt ...

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    be employed, so that electrostatic forces can operate against tension springs or mag-nets, and in this way, electrostatic meters can be made.An electrostatic device has the ability to measure alternating electric charges aswell as steady charges. This gives electrostatic meters an advantage over ...

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    AmmetersGetting back to electromagnetic deflection, and the workings of the galvanometer, youmight have thought by now that a magnetic compass doesn’t make a very convenienttype of meter. It has to be lying flat, and the coil has to be aligned with the compass nee-dle when there is no current. ...

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    overcome by the magnetic force, causes the needle to fly past the actual current levelbefore finally coming to rest at the correct reading.It is possible to use an electromagnet in place of the permanent magnet in the me-ter assembly. This electromagnet can be operated by the same current that fl...

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    voltage placed across it. Early electrical experimenters recognized that an ammetercould be used to measure voltage, since an ammeter is a form of constant-resistance circuit.If you connect an ammeter directly across a source of voltage—a battery, say—themeter needle will deflect. In fact, a ...

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    Another type of voltmeter uses the effect of electrostatic deflection, rather thanelectromagnetic deflection. You remember that electric fields produce forces, just as domagnetic fields. Therefore, a pair of plates will attract or repel each other if they arecharged. The electrostatic voltmeter m...

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    the appropriate voltage. The smallest deviation from the required voltage can cause abig error in the meter indication.The scale of an ohmmeter is nonlinear. That is, the graduations are not the sameeverywhere. Values tend to be squashed together towards the “infinity” end of the scale.52 Mea...

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    It can be difficult to interpolate for high values of resistance, unless the right scale is se-lected. Engineers and technicians usually connect an ohmmeter in a circuit with themeter set for the highest resistance range first; then they switch the range until the me-ter is in a part of the scale...

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    that a common VOM can measure is about 1 A. The maximum resistance is on the or-der of several megohms or tens of megohms. The lower limit of resistance indication isabout an ohm.FET and vacuum-tube voltmetersIt was mentioned that a good voltmeter will disturb the circuit under test as little as ...

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    much current for the house wiring to safely handle, and the fuse or breaker, detecting theexcess current, opened the circuit.Specialized wattmeters are necessary for the measurement of radio-frequency(RF) power, or for peak audio power in a high-fidelity amplifier, or for certain other spe-cializ...

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    Reading a pointer type utility meter is a little tricky, because you must think inwhatever direction (clockwise or counterclockwise) the scale goes. An example of apointer type utility meter is shown in Fig. 3-11. Read from left to right. For each littlemeter, take down the number that the pointe...

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    Frequency countersThe measurement of energy used by your home is an application to which digital me-tering is well suited. It’s easier to read the drum type, digital kilowatt-hour meter thanto read the pointer type meter. When measuring frequencies of signals, digital meteringis not only more c...

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    Light metersLight intensity is measured by means of a light meter or illumination meter. You mightthink that it’s easy to make this kind of meter by connecting a milliammeter to a solar(photovoltaic) cell. And this is, in fact, a good way to construct an inexpensive light me-ter (Fig. 3-14). Mo...

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    Sometimes, meters such as the one in Fig. 3-14 are used to measure infrared or ul-traviolet intensity. Different types of photovoltaic cells have peak sensitivity at differentwavelengths. Filters can be used to block out wavelengths that you don’t want the me-ter to detect.Pen recordersA meter ...

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    Technicians and engineers develop a sense of what a signal waveform should looklike, and then they can often tell, by observing the oscilloscope display, whether or notthe circuit under test is behaving the way it should. This is a subjective kind of“measurement, “ since it is qualitative as ...

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    C. Magnetic force. D. Electroscopic force.3. Suppose a certain current in a galvanometer causes the needle to deflect 20degrees, and then this current is doubled. The needle deflection:A. Will decrease.B. Will stay the same.C. Will increase.D. Will reverse direction.4. One important advantage of ...

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    B. Is placed between the negative pole of the supply and the circuit workingfrom the supply.C. Is placed between the positive pole of the supply and the circuit workingfrom the supply.D. Is placed in parallel with the circuit that works from the supply.10. Which of the following will not cause a ...

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    B. To make it impossible to use appliances that are too large for a givencircuit.C. To limit the amount of power that a circuit can deliver. D. To make sure the current is within safe limits.14. A utility meter’s motor speed works directly from:A. The number of ampere hours being used at the ti...

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    B. 6.6 V. C. 7. 0V. D. No way to tell; the meter is malfunctioning.64 Measuring devices3-18Illustration for quiz question 20.

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    4CHAPTERBasic dc circuitsYOU’VE ALREADY SEEN SOME SIMPLE ELECTRICAL CIRCUIT DIAGRAMS. SOME OFthese are the same kinds of diagrams, using the same symbols, that professional tech-nicians and engineers use. In this chapter, you’ll get more acquainted with this type ofdiagram. You’ll also lear...

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    four parallel lines, long-short-long-short. It’s not necessary to use more than four linesfor any battery, even though sometimes you’ll see six or eight lines. The symbols for acell and a battery are shown in Fig. 4-2.66 Basic dc circuits4-1At A, a fixed resistor. AtB, a two-terminal variable...

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    Schematic diagramsLook back through the earlier chapters of this book and observe the schematic dia-grams. These are all simple examples of how professionals would draw the circuits.There is no inscrutable gobbledygook to put in to make them into the sorts of circuitmaps that the most brilliant e...

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    Wiring diagramsThe difference between a schematic diagram and a wiring diagram is the amount ofdetail included. In a schematic diagram, the interconnection of the components isshown, but the actual values of the components are not necessarily indicated.You might see a diagram of a two-transistor ...

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    Ohm’s LawThe interdependence between current, voltage, and resistance is one of the most fun-damental rules, or laws, in electrical circuits. It is called Ohm’s Law, named after the sci-entist who supposedly first expressed it. Three formulas denote this law:EIRIE/RRE/IYou need only to rememb...

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    values can be assigned for the purpose of creating sample Ohm’s Law problems. Whilecalculating the current in the following problems, it is necessary to mentally “cover up”the meter.70 Basic dc circuits4-7Circuit for working Ohm’s Law problems.Problem 4-1Suppose that the dc generator (Fig...

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    you can do about it unless you are willing to use units of nanoamperes (nA), or bil-lionths of an ampere. Then you can say that the current is 186 nA.Voltage calculationsThe second use of Ohm’s Law is to find unknown voltages when the current and the re-sistance are known. For the following pro...

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    Problem 4-7If the voltmeter reads 24 V and the ammeter shows 3.0 A, what is the value of the po-tentiometer?Use the formula RE/I and plug in the values directly, because they are expressedin volts and amperes: R24/3.08. 0 .Note that you can specify this value to two significant figures, the eight...

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    Problem 4-10Suppose that the voltmeter reads 12 V and the ammeter shows 50 mA. What is thepower dissipated by the potentiometer?Use the formula PEI. First, convert the current to amperes, getting I0.050 A.(Note that the zero counts as a significant digit.) Then PEI120.050 0.60 W.You might say tha...

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    Problem 4-14Suppose the following resistances are hooked up in series with each other: 112 , 470, and 680 . What is the total resistance of the series combination (Fig. 4-8)?74 Basic dc circuits4-8Three resistors in series(Problem 4-14).Just add the values, getting a total of 112 + 470 + 680 1262...

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    When you have resistances in parallel and their values are all equal, the total resis-tance is equal to the resistance of any one component, divided by the number of com-ponents.Problem 4-16Suppose there are five resistors R1 through R5 in parallel, as shown in Fig. 4-9, all hav-ing a value of 4....

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    Sometimes, the total resistance of a series-parallel network is the same as the valueof any one of the resistors. This is always true if the components are identical, and arein a network called an n-by-n matrix. That means, when n is a whole number, there aren parallel sets of n resistors in seri...

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    component fails, and then a third. It’s hard to predict the current and power distribu-tion in an array when its resistor values are all different. So it’s hard to know whetherany of the components in such a matrix are going to burn out.If you need a resistance with a certain power-handling c...

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    2. A wiring diagram would most likely be found in: A. An engineer’s general circuit idea notebook.B. An advertisement for an electrical device. C. The service/repair manual for a radio receiver.D. A procedural flowchart.For questions 3 through 11, see Fig. 4-7.3. Given a dc voltage source deliv...

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    8. A source delivers 12 V and the current is 777 mA. Then the best expression forthe resistance is:A. 15 .B. 15.4 .C. 9.3 .D. 9.32 .9. The voltage is 250 V and the current is 8.0 mA. The power dissipated by thepotentiometer is:A. 31 mW.B. 31 W.C. 2.0 W.D. 2.0 mW.10. The voltage from the source is...

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    14. Suppose you have three resistors in parallel, each with a value of 68,000 .Then the total resistance is:A. 23 .B. 23 K.C. 204 .D. 0.2 M.15. There are three resistors in parallel, with values of 22 , 27 , and 33 . A12-V battery is connected across this combination, as shown in Fig. 4-11. What ...

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    B. 4 3 resistors.C. 4 4 resistors.D. 2 5 resistors.18. You have an unlimited supply of 1-W, 1000-resistors, and you need a 500-resistance rated at 7 W or more. This can be done by assembling:A. Four sets of two 1000-resistors in series, and connecting these four setsin parallel.B. Four sets of tw...

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    825CHAPTERDirect-current circuitanalysisIN THIS CHAPTER, YOU’LL LEARN MORE ABOUT DC CIRCUITS AND HOW THEYbehave. These principles apply to almost all circuits in utility ac applications, too.Sometimes it’s necessary to analyze networks that don’t have obvious practical use.But even a passiv...

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    Voltages across series resistances83would be increased still further. A third bulb would probably blow out almost right awayafter the string was plugged in.Voltages across series resistancesThe bulbs in the string of Fig. 5-1, being all the same, each get the same amount of volt-age from the sour...

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    How do you find the voltage across any particular resistor Rn in a circuit like the onein Fig. 5-2? Remember Ohm’s Law for finding voltage: EIR. The voltage is equal to theproduct of the current and the resistance. Remember, too, that you must use volts,ohms, and amperes when making calculation...

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    The voltage En across Rn 20Ω is En I(Rn)0.12202.4 V.Checking the total voltage, we add (5 1.2)(42.4)6.09.615.6 V. Thisrounds off to 16 V. Where did the extra volt come from?The above is an example of what can happen when you round off to significant fig-ures and then go through a problem a diff...

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    Currents through parallel resistancesRefer to the schematic diagram of Fig. 5-4. The resistors are called Rn. The total paral-lel resistance in the circuit is R. The battery voltage is E. The current in branch n, con-taining resistance Rn, is measured by ammeter A and is called In.The sum of all ...

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    First, find the total resistance. This is easy, because all the resistors have the samevalue. Just divide Rn120 by 12 to get R10Ω. Then the current, I, is found byOhm’s Law: IE/R12/101.2 A.Problem 5-4In the circuit of Fig. 5-4, what does the ammeter A say?This involves finding the current in ...

  • Page 109

    Power distribution in series circuitsLet’s switch back now to series circuits. This is a good exercise: getting used to thinkingin different ways and to changing over quickly and often.When calculating the power in a circuit containing resistors in series, all you needto do is find out the curr...

  • Page 110

    First find E 2, because you’ll be needing that number often: E 23.03.09.0.Then P19.0/220.4091 W, P29.0/470.1915 W, P39.0/680.1324 W. Thesecan be rounded off to P10.41 W, P20.19 W, and P30.13 W. But remember thevalues to four places for the next problem.In a parallel circuit, the total power con...

  • Page 111

    Kirchhoff reasoned that current must work something like water in a network ofpipes, and that the current going into any point has to be the same as the current goingout. This is true for any point in a circuit, no matter how many branches lead into or outof the point. Two examples are shown in F...

  • Page 112

    calculations and find that the total resistance, R, across the battery, E, is 66.67 Ω. ThenEIR66.673.0200 volts. (Some battery.)Problem 5-12In Fig. 5-5B, suppose each of the two resistors below point Z has a value of 100 Ω, andall three resistors above Z are 10.0 Ω. The current through each...

  • Page 113

    Problem 5-14In Fig. 5-6, suppose the battery provides 20 V. Let the resistors, having voltagedrops E1, E2, E3, and E4, have their ohmic values in the ratio 1:2:3:4 respectively.What is E3?This problem does not tell you the current in the circuit, nor the exact resistancevalues. But you don’t ne...

  • Page 114

    Resistances in series produce ratios of voltages, and these ratios can be tailored tomeet certain needs.When designing voltage divider networks, the resistance values should be as smallas possible, without causing too much current drain on the supply. In practice the opti-mum values depend on the...

  • Page 115

    Usually there are only two or three intermediate voltages in a voltage-divider net-work. So designing such a circuit isn’t as complicated as the above formulas might leadyou to think.The following problems are similar to those encountered by electronic engineers.Problem 5-15In a transistorized ...

  • Page 116

    QuizRefer to the text in this chapter if necessary. A good score is at least 18 correct answers.The answers are in the back of the book.1. In a series-connected string of holiday ornament bulbs, if one bulb gets shortedout, which of these is most likely?A. All the other bulbs will go out.B. The c...

  • Page 117

    B 5.0 V. C. 15 V.D. Not determinable from the data given.5. In the example of question 4 (Fig. 5-10), what is the current through R2?A. 6.8 mA.B. 43 mA.C. 150 mA.D. 6.8 A.6. In the example of question 4 (Fig. 5-10), what is the total current drawn fromthe source?A. 6.8 mA.B. 43 mA.C. 150 mA.D. 6....

  • Page 118

    A.11 mW.B.0.11 W.C.0.2 W. D. 6.5 mW.10. Three resistors are in parallel in the same configuration and with the samevalues as in problem 4 (Fig. 5-10). What is the power dissipated by the whole set?A.5.4 W.B.5.4 uW.C.650 W.D. 650 mW.11. In Fig. 5-10, the power dissipated by R1 is:A. 32 mW.B. 480 m...

  • Page 119

    A.4 V.B.8 V. C.16 V. D. Not determinable from the data given.16. Refer to Fig. 5-6. Let the resistances each be 3.3 KΩ and the battery 12 V. Ifthe plus terminal of a dc voltmeter is placed between R1 and R2 (with voltages E1and E2), and the minus terminal of the voltmeter is placed between R3 a...

  • Page 120

    6CHAPTERResistorsAS YOU’VE ALREADY SEEN, ANY ELECTRICAL DEVICE HAS SOME RESISTANCE; none is a perfect conductor. You’ve also seen some examples of circuits containing com-ponents designed to oppose the flow of current. This chapter more closely examines resistors—devices that oppose, contro...

  • Page 121

    of circuits. A radio transmitting amplifier would usually be biased differently than an os-cillator or a low-level receiving amplifier. Sometimes voltage division is required for bias-ing. Other times it isn’t necessary. Figure 6-1 shows a transistor whose base is biasedusing a pair of resistor...

  • Page 122

    power for the amplifier input. A resistor, or network of resistors, can dissipate this ex-cess so that the power amplifier doesn’t get too much drive.Bleeding off chargeIn a high-voltage, direct-current (dc) power supply, capacitors are used to smooth outthe fluctuations in the output. These ca...

  • Page 123

    It’s always a good idea to short out all filter capacitors, using a screwdriver with aninsulated handle, before working on a high-voltage dc power supply. I recall an instancewhen I was repairing the supply for a radio power amplifier. The capacitors were holdingabout 2 kV. My supervisor, not v...

  • Page 124

    Carbon-composition resistors dissipate power according to how big, physically,they are. Most of the carbon-composition resistors you see in electronics stores canhandle1⁄4 W or 1/2 W. There are 1/8-W units for miniaturized, low- power circuitry, and1-W or 2-W components for circuits where some ...

  • Page 125

    One of the advantages of wirewound resistors is that they can be made to have val-ues within a very close range; that is, they are precision components. Another advan-tage is that wirewound resistors can be made to handle large amounts of power. Somewirewounds might actually do well as electric h...

  • Page 126

    into a couple of ICs, or chips, whose total volume is about the same as that of the tip ofyour little finger. In 1930, a similar receiver would have been as large as a television set.Resistors can be fabricated onto the semiconductor chip that makes up an IC. Thethickness, and the types and conce...

  • Page 127

    Audio or logarithmic taperThere are some applications for which linear taper potentiometers don’t work well. Thevolume control of a radio receiver is a good example. Your ear/brain perceives sound levelaccording to the logarithm of its true level. If you use a linear taper potentiometer as thev...

  • Page 128

    This is a good time to sidetrack for a moment and exarnine how sound sensation ismeasured.The decibelPerceived levels of sound, and of other phenomena such as light and radio signals,change according to the logarithm of the actual power level. Units have been inventedto take this into account.The...

  • Page 129

    The fundamental unit of sound change is called the decibel, abbreviated dB. Achange of 1 dB is the minimum increase in sound level that you can detect, if you areexpecting it. A change of 1 dB is the minimum detectable decrease in sound volume,when you are anticipating the change. Increases in vo...

  • Page 130

    If a certain noise is given a loudness of 30 dB, it means it’s 30 dB above the thresh-old of hearing, or 1,000 times as loud as the quietest detectable noise. A noise at 60 dBis 1,000,000 times as powerful as the threshold of hearing. Sound level meters are usedto determine the dB levels of var...

  • Page 131

    Resistor valuesIn theory, a resistor can have any value from the lowest possible (such as a shaft of solidsilver) to the highest (open air). In practice, it is unusual to find resistors with valuesless than about 0.1 Ω, or more than about 100 MΩ.Resistors are manufactured in standard values t...

  • Page 132

    formula backwards, plugging in the power rating for P and the resistance of the unit forR, and solve for I. Or you can find the square root of P/R. Remember to use amperes forcurrent, ohms for resistance, and watts for power.The power rating for a given resistor can, in effect, be increased by us...

  • Page 133

    would need to make a 3 × 3 series-parallel network. And you can’t be sure that the oppos-ing effects will exactly balance. It would be better, in such a case, to make a 2 ×2 series-par-allel array of ordinary resistors.The color codeSome resistors have color bands that indicate their values a...

  • Page 134

    as shown in Fig. 6-12B. The first two bands represent numbers 0 through 9; the thirdband represents a multiplier of 10 to some power. For the moment, don’t worry aboutthe fourth and fifth bands. Refer to Table 6-1.The color code113Table 6-1 Resistor color codeNumeralMultiplierColor of band(Ba...

  • Page 135

    QuizRefer to the text in this chapter if necessary. A good score is at least 18 correct. Answersare in the back of the book.1. Biasing in an amplifier circuit:A. Keeps it from oscillating.B. Matches it to other amplifier stages in a chain.C. Can be done using voltage dividers.D. Maximizes current...

  • Page 136

    B. A linear-taper potentiometer. C. A logarithmic-taper potentiometer. D. A wirewound resistor.8. A volume control in a stereo compact-disc player would probably be:A. A set of switchable, fixed resistors.B. A linear-taper potentiometer.C. A logarithmic-taper potentiometer.D. A wirewound resistor...

  • Page 137

    14. Suppose a resistor is rated at 3.3 KΩ, plus or minus 5 percent. This means itcan be expected to have a value between:A. 2,970 and 3,630 Ω.B. 3,295 and 3,305 Ω.C. 3,135 and 3,465 Ω.D. 2.8 KΩ and 3.8 KΩ.15. A package of resistors is rated at 56 Ω, plus or minus 10 percent. You tes...

  • Page 138

    20. A resistor has three bands: gray, red, yellow. This unit can be expected to havea value within approximately what range? A. 660 KΩ to 980 KΩ.B. 740 KΩ to 900 KΩ.C. 7.4 KΩ to 9.0 KΩ.D. The manufacturer does not make any claim.Quiz117

  • Page 139

    7CHAPTERCells and batteriesONE OF THE MOST COMMON AND MOST VERSATILE SOURCES OF DC IS THE CELL.The term cell means self-contained compartment, and it can refer to any of various dif-ferent things in (and out of) science. In electricity and electronics, a cell is a unit sourceof dc energy. There a...

  • Page 140

    metals came into contact with certain chemical solutions, voltages appeared betweenthe pieces of metal. These were the first electrochemical cells.A piece of lead and a piece of lead dioxide immersed in an acid solution (Fig. 7-1)will show a persistent voltage. This can be detected by connecting ...

  • Page 141

    Other kinds of cells, like the lead-and-acid unit depicted above, can get their chem-ical energy back again. Such a cell is a secondary cell.Primary cells include the ones you usually put in a flashlight, in a transistor radio,and in various other consumer devices. They use dry electrolyte pastes...

  • Page 142

    from it, and this can be specified in watt hours or kilowatt hours. More often though it’sgiven in ampere hours (Ah).A battery with a rating of 2 Ah can provide 2 A for an hour, or 1 A for 2 hours. Or itcan provide 100 mA for 20 hours. Within reason, the product of the current in amperes,and th...

  • Page 143

    especially the nickel-cadmium type, should never be used until the current goes down tozero, because this can ruin them.122 Cells and batteries7-3A flat discharge curve. This is considered ideal.The area under the curve in Fig. 7-3 is the total capacity of the cell or battery inampere hours. This...

  • Page 144

    Alkaline cellsThe alkaline cell uses granular zinc for the negative electrode, potassium hydroxide asthe electrolyte, and a device called a polarizer as the positive electrode. The geometryof construction is similar to that of the zinc-carbon cell. An alkaline cell can work atlower temperatures t...

  • Page 145

    Band (CB) or ham radio. They’re also good for scanner radio receivers in portable loca-tions, for camping lamps, and for other medium-power needs.Miniature cells and batteriesIn recent years, cells and batteries—especially cells—have become available in many dif-ferent sizes and shapes besi...

  • Page 146

    to make a battery, the resulting voltage will be about 8.1 V rather than 9 V. One addi-tional cell can be added to the stack, yielding about 9.45 V.There has been some decrease in the popularity of mercury cells and batteries inrecent years. This is because of the fact that mercury is highly toxi...

  • Page 147

    buy two sets of cells and switch them every couple of hours of use, charging one set whileusing the other. Plug-in charger units cost only a few dollars.Types of NICAD cellsNickel-cadmium cells are made in several types. Cylindrical cells are the standardcells; they look like dry cells. Button ce...

  • Page 148

    Photovoltaic cells and batteriesThe photovoltaic cell is completely different from any of the electrochemical cells. It’salso known as a solar cell. This device converts visible light, infrared, and/or ultravioletdirectly into electric current.Solar panelsSeveral, or many, photovoltaic cells ca...

  • Page 149

    How large of a battery?You might get the idea that you can connect hundreds, or even thousands, of cells in se-ries and obtain batteries with fantastically high EMFs. Why not put 1,000 zinc-carboncells in series, for example, and get 1.5 kV? Or put 2,500 solar cells in series and get 1.25kV? Mayb...

  • Page 150

    There are several reasons why these schemes aren’t good ideas. First, high voltagesfor practical purposes can be generated cheaply and efficiently by power convertersthat work from 117-V or 234-V utility mains. Second, it would be difficult to maintain abattery of thousands, millions or billion...

  • Page 151

    QuizRefer to the text in this chapter if necessary. A good score is 18 correct. Answers are inthe back of the book.1. The chemical energy in a battery or cell:A. Is a form of kinetic energy.B. Cannot be replenished once it is gone.C. Changes to kinetic energy when the cell is used.D. Is caused by...

  • Page 152

    7. A 12-V auto battery is rated at 36 Ah. If a 100-W, 12-Vdc bulb is connectedacross this battery, about how long will the bulb stay lit, if the battery has beenfully charged?A. 4 hours and 20 minutes.B. 432 hours.C. 3.6 hours.D. 21.6 minutes.8. Alkaline cells:A. Are cheaper than zinc-carbon cell...

  • Page 153

    B. In a portable video camera/recorder. C. In an LCD wall clock. D. In a flashlight.14. A cell or battery that keeps up a constant current-delivering capability almostuntil it dies is said to have:A. A large ampere-hour rating.B. Excellent energy capacity.C. A flat discharge curve.D. Good energy ...

  • Page 154

    20. One reason why it is impractical to make an extrememly high-voltage batteryof cells is that:A. There’s a danger of electric shock.B. It is impossible to get more than 103.5 V with electrochemical cells.C. The battery would weigh to much.D. There isn’t any real need for such thing.Quiz133

  • Page 155

    8CHAPTERMagnetismTHE STUDY OF MAGNETISM IS A SCIENCE IN ITSELF. ELECTRIC AND MAGNETIC phe-nomena interact; a detailed study of magnetism and electromagnetism could easily filla book. Magnetism was mentioned briefly near the end of chapter 2. Here, the subjectis examined more closely. The intent i...

  • Page 156

    This solar wind literally “blows” the geomagnetic field out of shape, as shown in Fig. 8-1.At and near the earth’s surface, the lines of flux are not affected very much, and the geo-magnetic field is nearly symmetrical.Magnetic force1358-1The geomagnetic field is distorted by the solar wind...

  • Page 157

    of ferromagnetic material, the atoms in the material become lined up, so that the metal istemporarily magnetized. This produces a magnetic force between the atoms of the fer-romagnetic substance and those in the magnet.If a magnet is brought near another magnet, the force is even stronger. Not on...

  • Page 158

    Another experiment involves passing a current-carrying wire through the paper ata right angle, as shown in Fig. 8-3. The iron filings will be grouped along circles centeredat the point where the wire passes through the paper.Physicists consider magnetic fields to be comprised of flux lines. The i...

  • Page 159

    With a current-carrying wire, the magnetic field just goes around and around end-lessly, like a dog chasing its own tail.A charged electric particle, such as a proton, hovering in space, is a monopole, andthe electric flux lines around it aren’t closed (Fig. 8-4). A positive charge does not hav...

  • Page 160

    Dipoles and monopolesA pair of magnetic poles is called a dipole. A lone pole, like the positive pole in a pro-ton, is called a monopole.Magnetic monopoles do not ordinarily exist in nature. If they could somehow beconjured up, all sorts of fascinating things might happen. Scientists are research...

  • Page 161

    The ampere-turn and the gilbertWhen working with electromagnets, another unit is employed. This is the ampere-turn(At). It is a unit of magnetomotive force. A wire, bent into a circle and carrying 1 A ofcurrent, will produce 1 At of magnetomotive force. If the wire is bent into a loop having50 tu...

  • Page 162

    Just be sure all the wire turns go in the same direction. A large 6-V lantern batterycan provide plenty of dc to work the electromagnet. Never leave the coil connected tothe battery for more than a few seconds at a time. And never use a car battery for thisexperiment! (The acid might boil out.)Di...

  • Page 163

    PermeabilitySome substances cause the magnetic lines of flux to get closer together than they are inthe air. Some materials can cause the lines of flux to become farther apart than they arein the air.The first kind of material is ferromagnetic, and is of primary importance in mag-netism. Ferromag...

  • Page 164

    maximum; further increasing the current in the wire will not make the rod any more mag-netic. Now suppose that the current is shut off, and 19 gauss remain in the rod. Then theretentivity, Br, isBr = 100(19/135) = 100 0.14 = 14 percentVarious different substances have good retentivity; these are ...

  • Page 165

    that was magnetized, so that it could hold on to screws when installing or removingthem from hard-to-reach places.Permanent magnets are best made from materials with high retentivity. Magnetsare made by using a high-retentivity ferromagnetic material as the core of an electro-magnet for an extend...

  • Page 166

    When there is no current flowing in the coil, the steel rod is held down by the forceof gravity. But when a pulse of current passes through the coil, the rod is pulled forciblyupward so that it strikes the ringer plate. This plate is like one of the plates in a xylo-phone. The current pulse is sh...

  • Page 167

    Figure 8-9 is a simplified, cutaway drawing of a dc motor. One set of coils, called thearmature coil, goes around with the motor shaft. The other set of coils, called the fieldcoil, is stationary. The current direction is periodically reversed during each rotation bymeans of the commutator. This ...

  • Page 168

    The tape itself consists of millions of particles of iron oxide, attached to a plastic ormylar strip. A fluctuating magnetic field, produced by the recording head, polarizesthese particles. As the field changes in strength next to the recording head, the tapepasses by at a constant, controlled sp...

  • Page 169

    On a larger scale, the disk works differently than the tape, simply because of thedifference in geometry. On a tape, the information is spread out over a long span, andsome bits of data are far away from others. But on a disk, no two bits are ever fartherapart than the diameter of the disk. This ...

  • Page 170

    A full description of the way bubble memory systems are made, and the way theywork, is too advanced for this book. Bubble memory makes use of all the advantages ofmagnetic data storage, as well as the favorable aspects of electronic data storage. Ad-vantages of electronic memory include rapid sto...

  • Page 171

    6. Lines of magnetic flux are said to originate:A. In atoms of ferromagnetic materials.B. At a north magnetic pole.C. Where the lines converge to a point.D. In charge carriers.7. The magnetic flux around a straight, current-carrying wire:A. Gets stronger with increasing distance from the wire.B. ...

  • Page 172

    D. Disruption of microwave radio links.13. An ac electromagnet:A. Will attract only other magnetized objects. B. Will attract pure, unmagnetized iron.C. Will repel other magnetized objects. D. Will either attract or repel permanent magnets, depending on the polarity.14. An advantage of an electro...

  • Page 173

    C. Disks look better. D. Disks are less susceptible to magnetic fields.20. A bubble memory is best suited for:A. A large computer.B. A home video entertainment system.C. A portable cassette player.D. A magnetic disk.152 Magnetism

  • Page 174

    Test: Part oneDO NOT REFER TO THE TEXT WHEN TAKING THIS TEST. A GOOD SCORE IS AT LEAST 37 correct. Answers are in the back of the book. It’s best to have a friend check yourscore the first time, so you won’t memorize the answers if you want to take the testagain.1. An application in which an ...

  • Page 175

    C. Opposition to electrical current. D. Electrical conductance. E. Potential difference.4. A wiring diagram differs from a schematic diagram in that: A. A wiring diagram is less detailed. B. A wiring diagram shows component values.C. A schematic does not show all the interconnections between thec...

  • Page 176

    9. Which of the following correctly states Ohm’s Law?A. Volts equal amperes divided by ohms.B. Ohms equal amperes divided by volts.C. Amperes equal ohms divided by volts.D. Amperes equal ohms times volts.E. Ohms equal volts divided by amperes.10. The current going into a point in a dc circuit i...

  • Page 177

    E. Fluctuating.15. A resistor has a value of 680 ohms, and a tolerance of plus or minus 5 percent.Which of the following values indicates a reject?A. 648 Ω.B. 712 Ω.C. 699 Ω.D. 636 Ω.E. 707 Ω.16. A primitive device for indicating the presence of an electric current is:A. An electrometer...

  • Page 178

    D. Electronic. E. Static.21. The sum of the voltages, going around a dc circuit, but not including the powersupply, has:A. Equal value, and the same polarity, as the supply.B. A value that depends on the ratio of the resistances.C. Different value from, but the same polarity as, the supply.D. Equ...

  • Page 179

    C. An insulator. D. A resistor. E. A diamagnetic substance.27. Primary cells:A. Can be used over and over.B. Have higher voltage than other types of cells.C. All have exactly 1.500 V.D. Cannot be recharged.E. Are made of zinc and carbon.28. A rheostat:A. Is used in high-voltage and/or high-power ...

  • Page 180

    C. 1 V. D. 2 V. E. 3 V.33. A unit of electrical charge quantity is the:A. Volt.B. Ampere.C. Watt.D. Tesla.E. Coulomb.34. A unit of sound volume is:A. The volt per square meter.B. The volt.C. The watt hour.D. The decibel.E. The ampere per square meter.35. A 24-V battery is connected across a set o...

  • Page 181

    B. Electrostatic plates. C. A sensitive amplifier. D. High internal resistance. E. The highest possible full-scale value.39. The purpose of a bleeder resistor is to:A. Provide bias for a transistor.B. Serve as a voltage divider.C. Protect people against the danger of electric shock.D. Reduce the ...

  • Page 182

    44. A device commonly used for remote switching of wire communications signalsis:A. A solenoid.B. An electromagnet.C. A potentiometer.D. A photovoltaic cell.E. A relay.45. NICAD memory:A. Occurs often when NICADs are misused. B. Indicates that the cell or battery is dead. C. Does not occur very o...

  • Page 183

    D. 1.80 W.E. 4.50 W.50. The main problem with a bar-graph meter is that:A. Is isn’t very sensitive.B. It isn’t stable.C. It can’t give a very precise reading.D. You need special training to read it.E. It shows only peak values.162 Test: Part one

  • Page 184

    2PARTAlternating current

  • Page 185

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  • Page 186

    9CHAPTERAlternating currentbasicsDIRECT CURRENT (DC) IS SIMPLE. IT CAN BE EXPRESSED IN TERMS OF JUST TWOvariables: polarity (or direction), and magnitude. Alternating current (ac) is somewhatmore complicated, because there are three things that can vary. Because of the greaternumber of parameters...

  • Page 187

    Fig. 9-1 for a simple ac wave. The period of a wave can, in theory, be anywhere from a minuscule fraction of a second to many centuries. Radio-frequency currents reverse po-larity millions or billions of times a second. The charged particles held captive by the mag-netic field of the sun, and per...

  • Page 188

    The sine waveSometimes, alternating current has a sine-wave, or sinusoidal, nature. This meansthat the direction of the current reverses at regular intervals, and that thecurrent-versus time curve is shaped like the trigonometric sine function. The waveformin Fig. 9-1 is a sine wave.Any ac wave t...

  • Page 189

    Slow-rise, fast-decayAnother form of sawtooth wave is just the opposite, with a gradual positive-going slopeand a vertical negative-going transition. This type of wave is sometimes called a ramp,because it looks like an incline going upwards (Fig. 9-4). This waveshape is useful forscanning in tel...

  • Page 190

    Variable rise and decayYou can probably guess that sawtooth waves can have rise and decay slopes in an infinitenumber of different combinations. One example is shown in Fig. 9-5. In this case, thepositive-going slope is the same as the negative-going slope. This is a triangular wave.Complex and i...

  • Page 191

    Frequency spectrumAn oscilloscope shows a graph of magnitude versus time. Because time is on the hori-zontal axis, the oscilloscope is said to be a time-domain instrument.Sometimes you want to see magnitude as a function of frequency, rather than as afunction of time. This can be done with a spec...

  • Page 192

    Frequency spectrum1719-7At A, pure 60-Hz sine waveon spectrum analyzer. At B,60-Hz wave containingharmonics.9-8Modulated radio signal onspectrum analyzer

  • Page 193

    Little bits of a cycleEngineers break the ac cycle down into small parts for analysis and reference. One com-plete cycle can be likened to a single revolution around a circle.DegreesOne method of specifying the phase of an ac cycle is to divide it into 360 equal parts,called degrees or degrees of...

  • Page 194

    Phase differenceTwo ac waves might have exactly the same frequency, but they can still have differenteffects because they are “out of sync” with each other. This is especially true when acwaves are added together to produce a third, or composite, signal.If two ac waves have the same frequency...

  • Page 195

    Peak-to-peak amplitudeThe peak-to-peak (pk-pk) amplitude of a wave is the net difference between the pos-itive peak amplitude and the negative peak amplitude (Fig. 9-11). Another way of say-ing this is that the pk-pk amplitude is equal to the positive peak amplitude plus thenegative peak amplitud...

  • Page 196

    The name “root mean square” was not chosen just because it sounds interesting.It literally means that the value of a wave is mathematically operated on, by takingthe square root of the mean of the square of all its values. You don’t really have to beconcerned with this process, but it’s a...

  • Page 197

    “Hybrid” ac/dc combinations are not often generated deliberately. But such wave-forms are sometimes seen at certain points in electronic circuitry.The ac generator Alternating current is easily generated by means of a rotating magnet in a coil of wire(Fig. 9-14A), or by a rotating coil of wir...

  • Page 198

    When a load, such as a light bulb or heater, is connected to an ac generator, it be-comes more difficult to turn the generator. The more power needed from a generator,the greater the amount of power required to drive it. This is why it is not possible to con-nect a generator to, for instance, you...

  • Page 199

    sources of energy. Often, steam drives the turbines, and the steam is obtained via heatderived from the natural energy source.Why ac?You might wonder why ac is even used. Isn’t it a lot more complicated than dc?Well, ac is easy to generate from turbines, as you’ve just seen. Rotating coil-and...

  • Page 200

    2. The length of time between a point in one cycle and the same point in the nextcycle of an ac wave is the: A. Frequency. B. Magnitude.C. Period. D. Polarity.3. On a spectrum analyzer, a pure ac signal, having just one frequencycomponent,would look like:A. A single pip.B. A perfect sine wave.C. ...

  • Page 201

    B. 11,120 radians per second.C. 282 radians per second. D. Impossible to determine from the data given.9. A triangular wave:A. Has a fast rise time and a slow decay time.B. Has a slow rise time and a fast decay time.C. Has equal rise and decay rates.D. Rises and falls abruptly.10. Three-phase ac:...

  • Page 202

    15. In a perfect sine wave, the pk-pk value is:A. Half the peak value.B. The same as the peak value.C. 1.414 times the peak value.D. Twice the peak value.16. If a 45-Vdc battery is connected in series with the 117-V utility mains as shownin Fig. 9-15, the peak voltages will be:A. 210 V and 120 V....

  • Page 203

    C. Ac with one peak greater than the other.D Pulsating dc.20. An advantage of ac over dc in utility applications is:A. Ac is easier to transform from one voltage to another.B. Ac is transmitted with lower loss in wires.C. Ac can be easily gotten from dc generators.D. Ac can be generated with less...

  • Page 204

    10CHAPTERInductanceTHIS CHAPTER DELVES INTO DEVICES THAT OPPOSE THE FLOW OF AC BY temporarily storing some of the electrical energy as a magnetic field. Such devices arecalled inductors. The action of these components is known as inductance.Inductors often, but not always, consist of wire coils. ...

  • Page 205

    flowing in only part of the loop. The flux will increase over a period of a few seconds, asthe electrons get around the loop. Figure 10-2 is an approximate graph of the overallmagnetic field versus time. After about 5.5 seconds, current is flowing around the wholeloop, and the magnetic field has ...

  • Page 206

    is increased many times for a given length of wire compared with the flux produced bya single-turn loop. This is how inductors are made in practical electrical and electronicdevices.For any coil, the magnetic flux density is multiplied when a ferromagnetic core isplaced within the coil of wire. R...

  • Page 207

    You can just add up the values. Call the inductances of the individual components L1, L2,and L3, and the total inductance L. Then LL1L2L3404040120µH.186 Inductance10-3Inductors in series.Problem 10-2Suppose there are three inductors, with no mutual inductance, and their values are 20.0mH, 55.0 ...

  • Page 208

    Problem 10-3Suppose there are three inductors, each with a value of 40 µH, connected in parallelwith no mutual inductance, as shown in Fig. 10-4. What is the net inductance of the set?Interaction among inductors18710-4Inductors in parallel.Call the inductances L140µH, L240µH, and L340µH. Use ...

  • Page 209

    Mutual inductance can be minimized by using shielded wires and toroidal induc-tors. The most common shielded wire is coaxial cable. Toroidal inductors are dis-cussed a little later in this chapter.Coefficient of couplingThe coefficient of coupling, specified by the letter k, is a number ranging f...

  • Page 210

    Problem 10-6There are two coils with values L1835µH and L22.44 mH. They are connected inseries so that their coefficient of coupling is 0.922, acting so that the coils oppose eachother, as shown in Fig. 10-6. What is the net inductance of the pair?Air-core coils18910-5Illustration for Problem10-...

  • Page 211

    almost unlimited current-carrying capacity, just by using heavy-gauge wire and makingthe radius of the coil large. Air does not dissipate much energy in the form of heat; it isalmost lossless. For these reasons, air-core coils can be made highly efficient.Powdered-iron and ferrite coresFerromagne...

  • Page 212

    There are several advantages to toroidal coils over solenoidal, or cylindrical, ones.First, fewer turns of wire are needed to get a certain inductance with a toroid, as com-pared with a solenoid. Second, a toroid can be physically smaller for a given inductanceand current-carrying capacity. Third...

  • Page 213

    Pot coresThere is another way to confine the magnetic flux in a coil so that unwanted mutual in-ductance does not occur. This is to extend a solenoidal core completely around the out-side of the coil, making the core into a shell (Fig. 10-9). This is known as a pot core.Whereas in most inductors ...

  • Page 214

    Inductors at audio frequencyInductors at audio frequencies range in value from a few millihenrys up to about 1 H.They are almost always toroidally wound, or are wound in a pot core, or comprise partof an audio transformer.Inductors can be used in conjunction with moderately large values of capaci...

  • Page 215

    wavelength, in free space is just 75 cm, or a little more than 2 ft. In general, if f is the fre-quency in megahertz, then 1⁄4 wavelength (s) in free space, in centimeters, is given bys7500/fThe length of a quarter-wavelength section of transmission line is shortened fromthe free-space quarter ...

  • Page 216

    inductance will become larger as the frequency increases. At a certain limiting fre-quency, the inductance becomes infinite. Above that frequency, the line becomes ca-pacitive instead. You’ll learn about capacitance shortly.A detailed discussion of frequency, transmission line type and length, ...

  • Page 217

    B. The current flow is always large. C. The current flow is always small.D. Energy is stored and released quickly.4. A ferromagnetic core is placed in an inductor mainly to:A. Increase the current carrying capacity.B. Increase the inductance.C. Limit the current.D. Reduce the inductance.5. Induct...

  • Page 218

    C. 5 H. D. None of these.10. Two inductors, each of 100 µH, are in series. The coefficient of coupling is 0.40.The net inductance, if the coil fields reinforce each other, is:A. 50 µH.B. 120 µH.C. 200 µH.D. 280 µH.11. If the coil fields oppose in the foregoing series-connected arrangement, t...

  • Page 219

    D. The magnetic flux in a toroid is practically all within the core.16. A major feature of a pot-core winding is:A. High current capacity.B. Large inductance in small volume.C. Efficiency at very high frequencies.D. Ease of inductance adjustment.17. As an inductor core material, air:A. Has excell...

  • Page 220

    11CHAPTERCapacitanceELECTRICAL COMPONENTS CAN OPPOSE AC IN THREE DIFFERENT WAYS, TWO OFwhich you’ve learned about already.Resistance slows down the rate of transfer of charge carriers (usually electrons) by“brute force.” In this process, some of the energy is invariably converted from elect...

  • Page 221

    it will take awhile for the negative one to “fill up” with electrons, and it will take an equalamount of time for the other one to get electrons “sucked out.” Finally, however, the volt-age between the two plates will be equal to the battery voltage, and an electric field willexist in the...

  • Page 222

    Energy will be stored in this electric field. The ability of the plates, and of the spacebetween them, to store this energy is the property of capacitance. It is denoted by theletter C.Practical capacitorsIt’s out of the question to make a capacitor of the above dimensions. But two sheets, orst...

  • Page 223

    Capacitors in seriesWith capacitors, there is almost never any mutual interaction. This makes capacitorssomewhat easier to work with than inductors.Capacitors in series add together like resistors in parallel. If you connect two ca-pacitors of the same value in series, the result will be half the...

  • Page 224

    1/C210,000. Therefore, 1/C1,00010,00011,000, and C0. 000091 µF. Thisnumber is a little awkward, and you might rather say it’s 91 pF.In the above problem, you could have chosen pF to work with, rather than µF. In either case, there is some tricky decimal placement involved. It’s important to...

  • Page 225

    In this case, without even doing any calculations, you can say that the total is 100µF for practical purposes. The 100-pF unit is only a millionth of the capacitance of the100-µF component; therefore, the smaller capacitor contributes essentially nothing tothe composite total.Dielectric materia...

  • Page 226

    These capacitors can still sometimes be found in electronic equipment. They havevalues ranging from about 0.001 µF to 0.1 µF, and can handle low to moderate voltages,usually up to about 1000 V.Mica capacitorsWhen you were a child, you might have seen mica, a naturally occurring, transparentsubs...

  • Page 227

    For low values of capacitance, just one layer of ceramic is needed, and two metalplates can be glued to the disk-shaped porcelain, one on each side. This type of compo-nent is known as a disk-ceramic capacitor. Alternatively, a tube or cylinder of ceramiccan be employed, and metal ink applied to ...

  • Page 228

    Tantalum capacitors have high reliability and excellent efficiency. They are oftenused in military applications because they do not fail often. They can be used in au-dio-frequency and digital circuits in place of aluminum electrolytics.Semiconductor capacitorsA little later in this book, you’l...

  • Page 229

    Air variablesBy connecting two sets of metal plates so that they mesh, and by affixing one set to arotatable shaft, a variable capacitor is made. The rotatable set of plates is called the rotor, and the fixed set is called the stator. This is the type of component you mighthave seen in older radi...

  • Page 230

    If a section of transmission line is less than 1/4 wavelength long, and is left open atthe far end (rather than shorted out), it will act as a capacitor. The capacitance will in-crease with length.The most common transmission-line capacitor uses two telescoping sections oftubing. This is called a...

  • Page 231

    Therefore, a 10-percent capacitor can range from 10 percent less than its assignedvalue to 10 percent more.Problem 11-6A capacitor is rated at 0.001 µF, plus-or-minus 10 percent. What is the actual range ofcapacitances it can have?First, multiply 0.001 by 10 percent to get the plus-or-minus vari...

  • Page 232

    if interaction might produce trouble. This is why, if you’ve ever opened up a sophisti-cated communications radio, you might have seen numerous metal enclosures insidethe main box.QuizRefer to the text in this chapter if necessary. A good score is 18 correct. Answers are inthe back of the book....

  • Page 233

    B. 330 pF. C. 3300 pF.D. 33,000 pF.7. Five 0.050-µF capacitors are connected in parallel. The total capacitance is:A. 0.010 µF.B. 0.25 µF.C. 0.50 µF.D. 0.025 µF.8. If the same five capacitors are connected in series, the total capacitance will be:A. 0.010 µF.B. 0.25 µF.C. 0.50 µF.D. 0.025...

  • Page 234

    13. Which of the following is not a characteristic of mica capacitors?A. High efficiency.B. Small size.C. Capability to handle high voltages.D. Low loss.14. A disk ceramic capacitor might have a value of:A. 100 pF. B. 33 µF. C. 470 µF. D. 10,000 µF.15. A paper capacitor might have a value of:A...

  • Page 235

    20. A capacitor, rated at 330 pF, shows an actual value of 317 pF. How manypercent off is its value? A. 0.039.B. 3.9. C. 0.041. D. 4.1.214 Capacitance

  • Page 236

    12CHAPTERPhaseAN ALTERNATING CURRENT REPEATS THE SAME WAVE TRACE OVER AND OVER.Each 360-degree cycle is identical to every other. The wave can have any imaginableshape, but as long as the polarity reverses periodically, and as long as every cycle is thesame, the wave can be called true ac.In this...

  • Page 237

    If you freeze time at so-many-and-a-quarter seconds, say t446.25 seconds, thevoltage will be1 V. The wave will be exactly at its positive peak. If you stop time atso-many-and-three-quarter seconds, say t446.75 seconds, the voltage will be exactly at its negative peak, 1 V.At intermediate times, s...

  • Page 238

    Suppose that you graph the rate of change in the voltage of the wave in Fig. 12-1against time. What will this graph look like? It turns out that it will have a shape that isa sine wave, but it will be displaced to the left of the original wave by one-quarter of acycle. If you plot the relative ra...

  • Page 239

    it will stop and turn around again. This will go on and on, with a frequency of 1 Hz, or acomplete cycle per second, because you are swinging the ball around at one revolutionper second.218 Phase12-3Swinging ball and string.At A, as seen fromabove; at B, as seenfrom edge-on.If you graph the posit...

  • Page 240

    degrees. A sine wave can be represented as circular motion. Exact moments along thesine curve correspond to specific angles, or positions, around a circle.Figure 12-5 shows the way a rotating vector is used to represent a sine wave. At A,the vector points “east,” and this is assigned the valu...

  • Page 241

    The peak amplitude of the wave can be thought of in terms of the length of the vec-tor. In Fig. 12-5, time is represented by the angle counterclockwise from “due east,” andamplitude is independent of time. This differs from the more common rendition of thesine wave, such as the one in Fig. 12...

  • Page 242

    Radians of phaseAn angle of 1 radian is about 57.3 degrees. A complete circle is 6.28 radians around. Ifa wave has a frequency of f Hz, then the vector goes through 1 radian of phase every1/(57.3f) seconds. The number of radians per second for an ac wave is called the angular frequency.Radians ar...

  • Page 243

    If two sine waves are in phase coincidence, the peak amplitude of the resultant wave,which will also be a sine wave, is equal to the sum of the peak amplitudes of the two com-posite waves. The phase of the resultant is the same as that of the composite waves.Phase oppositionWhen two waves begin e...

  • Page 244

    Suppose there are two sine waves, wave X and wave Y, with identical frequency. Ifwave X begins a fraction of a cycle earlier than wave Y, then wave X is said to be lead-ing wave Y in phase. For this to be true, X must begin its cycle less than 180 degreesbefore Y. Figure 12-9 shows wave X leading...

  • Page 245

    Lagging phaseSuppose that wave X begins its cycle more than 180 degrees, but less than 360 degrees,ahead of wave Y. In this situation, it is easier to imagine that wave X starts its cycle laterthan wave Y, by some value between 0 and 180 degrees. Then wave X is not leading, butinstead is lagging,...

  • Page 246

    Vector diagrams of phase relationshipsThe circular renditions of sine waves, such as are shown in the four drawings of Fig.12-5, are well suited to showing phase relationships.If a sine wave X is leading a sine wave Y by some number of degrees, then the twowaves can be drawn as vectors, with vect...

  • Page 247

    QuizRefer to the text in this chapter if necessary. A good score is 18 correct. Answers are inthe back of the book.1. Which of the following is not a general characteristic of an ac wave?A. The wave shape is identical for each cycle.B. The polarity reverses periodically.C. The electrons always fl...

  • Page 248

    7. A wave has a frequency of 300 kHz. One complete cycle takes:A.1⁄300 second.B. 0.00333 second.C.1⁄3,000 second.D. 0.00000333 second.8. If a wave has a frequency of 440 Hz, how long does it take for 10 degrees ofphase?A. 0.00273 second.B. 0.000273 second.C. 0.0000631 second.D. 0.00000631 sec...

  • Page 249

    B. Wave Y is1⁄4 cycle behind wave X.C. Wave Y is1⁄8 cycle behind wave X.D. Wave Y is1⁄16 cycle ahead of wave X.14. If wave X lags wave Y by1⁄3 cycle, then:A. Y is 120 degrees earlier than X.B. Y is 90 degrees earlier than X.C. Y is 60 degrees earlier than X.D. Y is 30 degrees earlier than...

  • Page 250

    17. In vector diagrams such as those of Fig. 12-13, length of the vector represents:A. Average amplitude.B. Frequency.C. Phase difference.D. Peak amplitude.Quiz22912-13Illustration for quiz questions 16 through 20.18. In vector diagrams such as those of Fig. 12-13, the angle between two vectorsre...

  • Page 251

    19. In vector diagrams such as those of Fig. 12-13, the distance from the center ofthe graph represents:A. Average amplitude.B. Frequency.C. Phase difference.D. Peak amplitude.20. In diagrams like those of Fig. 12-13, the progression of time is sometimesdepicted as:A. Movement to the right.B. Mov...

  • Page 252

    13CHAPTERInductive reactanceIN DC CIRCUITS, RESISTANCE IS A SIMPLE THING. IT CAN BE EXPRESSED AS Anumber, from zero (a perfect conductor) to extremely large values, increasing withoutlimit through the millions, billions, and even trillions of ohms. Physicists call resistancea scalar quantity, bec...

  • Page 253

    You can make an electromagnet, as you’ve already seen, by passing dc through acoil wound around an iron rod. But there will still be a large, constant current in the coil.The coil will probably get more or less hot, as energy is dissipated in the resistance ofthe wire. The battery, too, or powe...

  • Page 254

    At high ac frequencies, the current through the coil will have difficulty followingthe voltage placed across the coil. Just as the coil starts to “think” that it’s making agood short circuit, the ac voltage wave will pass its peak, go back to zero, and then tryto pull the electrons the othe...

  • Page 255

    Problem 13-2What will be the inductive reactance of the above coil if the supply is a battery that sup-plies pure dc?Because dc has a frequency of zero, XL6.2800. 50 0. That is, there willbe no inductive reactance. Inductance doesn’t generally have any practical effect withpure dc.Problem 13-3I...

  • Page 256

    XL3Ω, then the complex impedance is 0 j3, and is at the point (0, 3) on the RLplane. These points, and others, are shown in Fig. 13-6.In real life, all coils have some resistance, because no wire is a perfect conductor.All resistors have at least a tiny bit of inductive reactance, because they ...

  • Page 257

    In Fig. 13-6, there are four different points shown. Each one is represented by acertain distance to the right of the origin (0,0), and a specific distance upwards from theorigin. The first of these is the resistance, R, and the second is the inductive reactance,XL. Thus, the RL combination is a ...

  • Page 258

    Current lags voltageInductance, as you recall, stores electrical energy as a magnetic field. When a voltage isplaced across a coil, it takes awhile for the current to build up to full value.When ac is placed across a coil, the current lags the voltage in phase.Pure inductanceSuppose that you plac...

  • Page 259

    Inductance and resistanceWhen the resistance in a resistance-inductance circuit is significant compared with theinductive reactance, the current lags the voltage by something less than 90 degrees(Fig. 13-9). If R is small compared with XL, the current lag is almost 90 degrees; as Rgets larger, th...

  • Page 260

    Pure resistanceAs the resistance in an RL circuit becomes large with respect to the inductive reac-tance, the angle of lag gets smaller and smaller. The same thing happens if the inductivereactance gets small compared with the resistance. When R is many times greater thanXL, whatever their actual...

  • Page 261

    How much lag?If you know the ratio of the inductive reactance to the resistance, XL/R, in an RL circuit,then you can find the phase angle. Of course, you can find the angle of lag if you knowthe actual values of XL and R.Pictorial methodIt isn’t necessary to construct an entire RL plane to find...

  • Page 262

    Measure the angle between the slanted line and the horizontal, or R, axis. Extendone or both of the lines if necessary in order to get a good reading on the protractor. Thisangle will be between 0 and 90 degrees, and represents the phase angle in the RL circuit.The actual vector, RjXL , is found ...

  • Page 263

    Problem 13-4The inductive reactance in an RL circuit is 680 Ω, and the resistance is 840 Ω. What isthe phase angle?Find the ratio XL/R680/840. The calculator will display something like0.809523809. Find the arctangent, or tan 1, getting a phase angle of 38.99099404 de-grees (as shown on the c...

  • Page 264

    This requires that XL be found over again, for the new frequency. Suppose you de-cide to use megahertz, so it will go nicely in the formula with microhenrys. A frequencyof 10 kHz is the same as 0.010 MHz. Calculating, you get XL6.28fL6.280.010906.280.905.65Ω. The ratio XL /R is then 5.65/10 0. ...

  • Page 265

    6. A coil has an inductance of 400 µH. Its reactance is 33 Ω. What is thefrequency?A. 13 kHz.B. 0.013 kHz.C. 83 kHz.D. 83 MHz.7. An inductor has XL555Ω at f132 kHz. What is L?A. 670 mH.B. 670 µH.C. 460 mH.D. 460 µH.8. A coil has L689µH at f990 kHz. What is XL?A. 682Ω.B. 4.28 Ω.C. 4.28...

  • Page 266

    C. Corresponds to a unique resistance. D. All of the above.13. A vector is a quantity that has: A. Magnitude and direction. B. Resistance and inductance. C. Resistance and reactance.D. Inductance and reactance.14. In an RL circuit, as the ratio of inductive reactance to resistance, XL /R,decrease...

  • Page 267

    19 An RL circuit consists of a 100-µH inductor and a 100-Ω resistor. What is thephase angle at a frequency of 200 kHz?A. 45.0 degrees.B. 51.5 degrees.C. 38.5 degrees.D. There isn’t enough data to know.20. An RL circuit has an inductance of 88 mH. The resistance is 95 Ω. What is thephase a...

  • Page 268

    14CHAPTERCapacitive reactanceINDUCTIVE REACTANCE IS SOMETHING LIKE RESISTANCE, IN THE SENSE THAT ITis a one-dimensional, or scalar, quantity that can vary from zero upwards without limit.Inductive reactance, like resistance, can be represented by a ray, and is measured inohms.Inductive reactance ...

  • Page 269

    might take awhile for them to become fully charged. The current, once the plates arecharged, will be zero.248 Capacitive reactance14-2A capacitor connectedacross a source of dc.If you put some insulating material, such as glass, between the plates, their mutualvoltage will not change, although th...

  • Page 270

    As you increase the frequency of the ac voltage source, there will come a point atwhich the plates do not get charged up very much before the source polarity reverses.The set of plates will be “sluggish.” The charge won’t have time to get established witheach ac cycle.At high ac frequencies...

  • Page 271

    Capacitive reactance also varies inversely with the actual value of capacitance,given a fixed frequency. Therefore, the function of XC vs C also appears as a curve that“blows up” as the capacitance approaches zero.The negative of Xc is inversely proportional to frequency, and also to capacita...

  • Page 272

    In this problem, you need to put the numbers in the formula and solve for the un-known C. Begin with the equation 1001/(6.2810.0C)Dividing through by 100, you get:11/(62810.0C)Multiply each side of this by C, and you obtain:C1/(62810.0)This can be solved easily enough. Divide out C1/6280 on your ...

  • Page 273

    possibility that there might be reactance in the circuit, and that you’re working in two di-mensions. It also underscores the fact that the impedance is a pure resistance.If you have a pure capacitive reactance, say XC4Ω, then the complex imped-ance is 0 j4, and this is at the point (0, 4) on...

  • Page 274

    Vectors in the RC planeIf you work much with engineers, or if you plan to become one, you’ll get familiar withthe RC plane, just as you will with the RL plane. Recall from the last chapter that RL im-pedances can be represented as vectors. The same is true for RC impedances.In Fig. 14-6, there ...

  • Page 275

    Current leads voltageCapacitance stores energy in the form of an electric field. When a current is driventhrough a capacitor, it takes a little time before the plates can fully charge to the full po-tential difference of the source voltage.When an ac voltage source is placed across a capacitor, t...

  • Page 276

    Capacitance and resistanceWhen the resistance in a resistance-capacitance circuit is significant compared with thecapacitive reactance, the current leads the voltage by something less than 90 degrees(Fig. 14-9). If R is small compared with XC, the difference is almost a quarter of a cycle.As R ge...

  • Page 277

    The value of R in an RC circuit might increase relative to XC because resistance isdeliberately put into a circuit. Or, it might happen because the frequency becomes solow that XC rises to a value comparable with the leakage resistance of the capacitor. Ineither case, the situation can be represe...

  • Page 278

    Pictorial methodYou can use a protractor and a ruler to find phase angles for RC circuits, just as you didwith RL circuits, as long as the angles aren’t too close to 0 or 90 degrees.First, draw a line somewhat longer than 10 cm, going from left to right on the pa-per. Then, use the protractor t...

  • Page 279

    1 to get the RC phase angle. That is, if the protractor shows 27 degrees, the RC phaseangle is 27 degrees.The actual vector is found by constructing a rectangle using the origin and your twohash marks, making new perpendicular lines to complete the figure. The vector is thediagonal of this rectan...

  • Page 280

    Problem 14-4The capacitive reactance in an RC circuit is 3800Ω, and the resistance is 7400 Ω.What is the phase angle?Find the ratio XC /R3800/7400. The calculator win display something like0.513513513. Find the arctangent, or tan 1, getting a phase angle of 27.18111109 de-grees on the calcula...

  • Page 281

    B. The value of XC decreases negatively. C. The value of XC does not change. D. You can’t say what happens to XC without more data.3. As the frequency of a wave gets lower, all other things being equal, the value ofXC for a capacitor: A. Increases negatively.B. Decreases negatively. C. Does not...

  • Page 282

    9. A capacitor has C4700µF and XC33Ω. What is f?A. 1.0 Hz.B. 10 Hz.C. 1.0 kHz.D. 10 kHz.10. Each point in the RC plane:A. Corresponds to a unique inductance.B. Corresponds to a unique capacitance.C. Corresponds to a unique combination of resistance and capacitance.D. Corresponds to a unique co...

  • Page 283

    C. 0 degrees. D.90 degrees.16. If the ratio of XC/R is 1, the phase angle is:A. 0 degrees.B.45 degrees.C.90 degrees.D. Impossible to find; there’s not enough data given.17. In Fig. 14-13, the impedance shown is:A. 8.02 j323.B. 323 j8.02.C. 8.02 j323.D. 323 j8.02.262 Capacitive reactance14-13Ill...

  • Page 284

    B. About 60 degress, from the looks of it.C. 58.9 degrees.D.88.6 degrees.19. An RC circuit consists of a 150-pF capacitor and a 330 Ω resisitor in series.What is the phase angle at a frequency of 1.34 MHz?A. –67.4 degrees.B. –22.6 degrees.C. –24.4 degrees.D. –65.6 degrees.20. An RC circ...

  • Page 285

    15CHAPTERImpedance andadmittanceYOU’VE SEEN HOW INDUCTIVE AND CAPACITIVE REACTANCE CAN BE REPRE-sented along a line perpendicular to resistance. In this chapter, you’ll put all three ofthese quantities—R, XL, and XC—together, forming a complete, working definition ofimpedance. You’ll al...

  • Page 286

    realm of numbers. Mathematically, it’s as real as the real numbers. But the original term“imaginary” stuck, so that this number carries with it a mysterious aura.It’s not important, in this context, to debate the reality of the abstract, but to reas-sure you that imaginary numbers are not...

  • Page 287

    Subtracting complex numbers works similarly. The difference (4 j7)(45j83) is found by multiplying the second complex number by 1 and then adding the re-sult, getting (4 j7)( 1(45j83)(4j7)( 45j83)41j90.The general formula for the sum of two complex numbers (ajb) and (cjd) is(ajb)(cjd)(ac)j(bd)The ...

  • Page 288

    notational convention, and that is all. (It’s also a somewhat humorous illustration of the dif-ferent angle that an engineer takes in approaching a problem, as opposed to a mathemati-cian.)Complex number vectorsComplex numbers can also be represented as vectors in the complex plane. This givese...

  • Page 289

    In the case of a pure real number aj0, the absolute value is simply the numberitself, a, if it is positive, and a if a is negative.In the case of a pure imaginary number 0jb, the absolute value is equal to b ifb (which is a real number) is positive, and b if b is negative.If the number is neither...

  • Page 290

    Problem 15-1Find the absolute value of the complex number 22 – j0.Note that this is a pure real. Actually, it is the same as 22j0, because j0 = 0.Therefore, the absolute value of this complex number is –(–22)22.Problem 15-2Find the absolute value of 0 j34.This is a pure imaginary number. Th...

  • Page 291

    way that cannot generally occur with resistance. Capacitors act like “negative induc-tors.” Interesting things happen when capacitors and inductors are combined, which isdiscussed in the next couple of chapters.Reactance can vary from extremely large negative values, through zero, to ex-treme...

  • Page 292

    get longer. If R remains constant and XL gets larger, the vector will also grow longer. IfR stays the same as XC gets larger (negatively), the vector will grow longer yet again.Think of the point ajb, or RjX, moving around in the plane, and imaginewhere the corresponding points on the axes lie. T...

  • Page 293

    Absolute-value impedanceThere will be times when you’ll hear that the “impedance” of some device or componentis a certain number of ohms. For example, in audio electronics, there are “8-Ω” speak-ers and “600-Ω” amplifier inputs. How can manufacturers quote a single number for aq...

  • Page 294

    impedance. It is abbreviated Zo, and is a specification of transmission lines. It can always be expressed as a positive real number.Transmission linesAny time that it is necessary to get energy or signals from one place to another, a trans-mission line is required. These almost always take either...

  • Page 295

    In general, Zo increases as the wire diameter gets smaller, and decreases as the wirediameter gets larger, all other things being equal.In a coaxial line, the thicker the center conductor, the lower the Zo if the shieldstays the same size. If the center conductor stays the same size and the shiel...

  • Page 296

    Imagine that you have a 300-Ω television antenna, and you want the best possi-ble reception. You purchase “300-Ω” ribbon line, with a value of Zo that has been op-timized by the manufacturer for use with antennas whose impedances are close to300j0.For a system having an “impedance” of...

  • Page 297

    Remembering that 100 pF 0. 000100 µF, you can substitute in this formula for f3.00 and C0.000100, gettingXC1/(6.283.000.000100)1/0.001884531Ωj531The susceptance, BC, is equal to l/XC. Thus, BC1/( j531)j0.00188. Remem-ber that capacitive susceptance is positive. This can “short-circuit” any...

  • Page 298

    Admittance is the complex composite of conductance and susceptance. Thus, ad-mittance takes the formYGjBThe j factor might be negative, of course, so there are times you’ll write YGjB.Parallel circuitsRecall how resistances combine with reactances in series to form complex impedances?In chapter...

  • Page 299

    Formula for conductanceAs you move out towards the right (“east”) along the G, or conductance, axis of the GBplane, the conductance improves, and the current gets greater, but only for dc. The for-mula for G is simplyG1/Rwhere R is the resistance in ohms and G is the conductance in siemens, a...

  • Page 300

    When you move upwards (“north”) along the jB axis from the origin, you haveever-increasing capacitive susceptance. The formula for this quantity, BC, isBC6.28fL siemenswhere f is in Hertz and C is in farads. The value of B is in siemens. Alternatively, you canuse frequency values in megahertz...

  • Page 301

    Think in two dimensions. Draw your own RX and GB planes. (Be thankful there areonly two dimensions, and not three! Some scientists need to deal in dozens of dimensions.)If you want to be an engineer, you’ll need to know how to handle these expressions.If you plan to manage engineers, you’ll w...

  • Page 302

    B. Can never be positive. C. Might be either positive or negative. D. Is equal to j.2. A complex number:A. Is the same thing as an imaginary number.B. Has a real part and an imaginary part.C. Is one-dimensional.D. Is a concept reserved for elite imaginations.3. What is the sum of 3 j7 and 3j7?A. ...

  • Page 303

    C. A pure capacitance. D. An inductance combined with a resistance.9. What is the absolute-value impedance of 3.0 j6.0?A. Z9.0Ω.B. Z3.0Ω.C. Z45Ω.D. Z6.7Ω.10. What is the absolute-value impedance of 50 j235?A. Z240Ω.B. Z58,000Ω.C. Z285Ω.D. Z185Ω.11. If the center conductor of a coa...

  • Page 304

    15. Susceptance and conductance add to form:A. Impedance.B. Inductance.C. Reactance.D. Admittance.16. Absolute-value impedance is equal to the square root of:A. G2B2B. R2X2.C. Zo.D. Y.17. Inductive susceptance is measured in: A. Ohms. B. Henrys. C. Farads. D. Siemens.18. Capacitive susceptance is...

  • Page 305

    16CHAPTERRLC circuit analysisWHENEVER YOU SEE AC CIRCUITS WITH INDUCTANCE AND/OR CAPACITANCE ASwell as resistance, you should switch your mind into “2D” mode. You must be ready todeal with two-dimensional quantities.While you can sometimes talk and think about impedances as simple ohmic value...

  • Page 306

    Problem 16-1A coil and capacitor are connected in series, with jXLj200 and jXCj150. What isthe net reactance vector jX?Just add the values jXjXLjXCj200( j150)j(200150)j50. Thisis an inductive reactance, because it is positive imaginary.Problem 16-2A coil and capacitor are connected in series, wit...

  • Page 307

    This is a net capacitive reactance. There is no resistance in this circuit, so the imped-ance vector is 0 j73.Problem 16-4What is the net reactance vector jX for the above combination at a frequency of f10.0MHz?First calculatejXLj6.28fLj(6.28× 10.0× 5.00)j314Then calculatejXCj(1/(6.28fC))j(l/(6...

  • Page 308

    Formula for complex impedances in seriesGiven two impedances, Z1R1jX1 and Z2R2jX2, the net impedance Z of thesein series is their vector sum, given byZ(R1R2)j(X1X2)The reactances X1 and X2 might both be inductive; they might both be capacitive; orone might be inductive and the other capacitive.Co...

  • Page 309

    Calculating a vector sum using the formula is easier than doing it geometrically witha parallelogram. The arithmetic method is also more nearly exact. The resistance andreactance components add separately. That’s all there is to it.Series RLC circuitsWhen a coil, capacitor, and resistor are con...

  • Page 310

    Megahertz and microhenrys go together in the formula. As for XC, recall the formulaXC1/(6.28fC). Convert 220 pF to microfarads to go with megahertz in the formulaC0.000220 µF. ThenjXCj(l/(6.28× 7.15× 0.000220))j101Now, you can consider the resistance and the inductive reactance to go together,...

  • Page 311

    Problem 16-9A coil and capacitor are connected in parallel, with jBLj0.05 and jBCj0.08. Whatis the net admittance vector?Just add the values jBjBLjBCj0.05j0.08j0.03. This is a capacitivesusceptance, because it is positive imaginary. The admittance vector is 0 j0.03.Problem 16-10A coil and capacit...

  • Page 312

    This is a net inductive susceptance. There is no conductance in this circuit, so the ad-mittance vector is 0 – j0.00286.Problem 16-12What is the net admittance vector for the above combination at a frequency of f 5.31MHz?First calculatejBLj(l/(6.28fL)j(l/(6.28× 5.31× 6.00))j0.00500Then calcul...

  • Page 313

    The susceptances B1 and B2 might both be inductive; they might both be capacitive; orone might be inductive and the other capacitive.Parallel GLC circuitsWhen a coil, capacitor, and resistor are connected in parallel (Fig. 16-7), the resistorshould be thought of as a conductor, whose value in sie...

  • Page 314

    0.1, and the susceptance component of –j0.010j0.020j0.010. Therefore, the ad-mittance vector is 0.1 j0.010.Problem 16-14A resistor, coil, and capacitor are connected in parallel with G0.0010 siemens, jBLj0.0022 and jBCj0.0022. What is the net admittance vector?Again, consider the resistor to be...

  • Page 315

    1/R1/10.00.100.) Let the capacitance alone be the other vector, 0 j0.0100. Thenthe sum is 0.100 – j0.0100j0.01000. 100 j0. This is a pure conductance of 0.100siemens.Converting from admittance to impedanceThe GB plane is, as you have seen, similar in appearance to the RX plane, although math-em...

  • Page 316

    Proceed by the steps as numbered above.1. G1/R1/10.00.100.2. BL1/(6.28fL)1/(6.28× 1.00× 10.0) = 0.0159.3. BC6.28fC6.28× 1.00× 0.0008200.00515. (Remember to convertthe capacitance to microfarads, to go with megahertz.)4. BBLBC0.01590.005150.0108.5. First find G 2 B20.1002(-0.0108)20.010117. (G...

  • Page 317

    An example of a “complicated” series RLC circuit is shown in Fig. 16-8A. The equiv-alent circuit, with just one resistor, one capacitor, and one coil, is shown in Fig. 16-813.296 RLC circuit analysis16-8At A, a “complicated” series RLC circuit; at B, thesame circuit simplified.Parallel co...

  • Page 318

    Reducing complicated RLC circuits29716-9At A, a “complicated” parallel RLC circuit; at B, the same circuit simplified.16-10A series-parallel RLCnightmare.

  • Page 319

    Another way to find the complex impedance here would be to actually build the cir-cuit, connect a signal generator to it, and measure R and X directly with an impedancebridge. Because “the proof of the pudding is in the eating,” a performance test musteventually be done anyway, no matter how ...

  • Page 320

    The absolute-value impedance for a parallel RLC circuit, in which the resistance isR and the reactance is X, is defined by the formula:Z 2(RX)2/(R2X2)Thus, Z is equal to RX divided by the square root of R2 X2.Problem 16-20A series RX circuit (Fig. 16-11) has R50.0Ω of resistance and X 50.0Ω o...

  • Page 321

    be concerned with the geometry of the vectors in this situation. It’s enough to under-stand that the vectors don’t fall along a single line, and this is why the voltages don’t addarithmetically.Problem 16-22A series RX circuit (Fig. 16-11) has R10.0Ω and a net reactance X40.0Ω. The ap-p...

  • Page 322

    If you want to study the geometrical details of the voltage and current vectors in se-ries and parallel RX circuits, a good circuit theory text is recommended.One of the most important practical aspects of ac circuit theory involves the waysthat reactances, and complex impedances, behave when you...

  • Page 323

    C. 300 j142.D. 330 j16.8.6. A coil has an inductance of 3.00 µH and a resistance of 10.0 Ω in its winding. Acapacitor of 100 pF is in series with this coil. What is RjX at 10.0 MHz?A. 10 j3.00.B. 10 j29.2.C. 10 j97.D. 10 j348.7. A coil has a reactance of 4.00 Ω. What is the admittance vector...

  • Page 324

    11. A coil of 3.50 µH and a capacitor of 47.0 pF are in parallel. The frequency is9.55 MHz. There is nothing else in series or parallel with these components. What isthe admittance vector?A. 0 j0.00282.B. 0 – j0.00194.C. 0 j0.00194.D. 0 – j0.00758.12. A vector pointing “southeast” in the...

  • Page 325

    C. 46.2 j14.9.D. 46.2 j14.9.17. A series circuit has 99.0 Ω of resistance and 88.0 Ω of inductive reactance. Anac rms voltage of 117 V is applied to this series network. What is the current?A. 1.18 A.B. 1.13 A.C. 0.886 A.D. 0.846 A.18. What is the voltage across the reactance in the above exa...

  • Page 326

    17CHAPTERPower and resonance inac circuitsYOU HAVE LEARNED HOW CURRENT, VOLTAGE, AND RESISTANCE BEHAVE IN ac circuits. How can all this theoretical knowledge be put to practical use?One of the engineer’s biggest challenges is the problem of efficient energy transfer.This is a major concern at ...

  • Page 327

    (mW or thousandths of watts), microwatts (µW or millionths of watts), or nanowatts(nW or billionths of watts).Volt-amperesIn dc circuits, and also in ac circuits having no reactance, power can be defined thisway: Power is the product of the voltage across a circuit or component, times thecurrent...

  • Page 328

    Imaginary powerIf an ac circuit contains reactance, things get interesting. The rate of energy expendi-ture is the same as the VA power in a pure resistance. But when inductance and/or ca-pacitance exists in an ac circuit, these two definitions of power part ways. The VApower becomes greater than...

  • Page 329

    antenna, you might say you’re “feeding power” through the cable to the antenna. Every-body says this, even engineers and technicians. What’s moving along the cable is imag-inary power, not true power. True power always involves a change in form, such asfrom electrical current and voltage ...

  • Page 330

    A reactance causes ac current to shift in phase, so that it is no longer exactly in stepwith the voltage. In a circuit with inductive reactance, the current lags the voltage by upto 90 degrees, or one-quarter cycle. In a circuit with capacitive reactance, the currentleads the voltage by up to 90 ...

  • Page 331

    Engineers often strive to eliminate, or at least minimize, the reactance in a circuit.This is particularly true for radio antenna systems, or when signals must be sent overlong spans of cable. It is also important in the design of radio-frequency amplifiers. To alesser extent, minimizing the reac...

  • Page 332

    angle is 0 degrees, because the current is in phase with the voltage. Using your calcula-tor, find cos 0 1. Therefore, PF1100 percent. The vector for this case is shownin Fig. 17-5.Calculation of power factor31117-6Phase angle for a purecapacitive impedance0− j40.17-5Phase angle for a pureresis...

  • Page 333

    Problem 17-3A circuit contains a resistance of 50 Ω and an inductive reactance of 50 Ω in series.What is the power factor?The phase angle in this case is 45 degrees (Fig. 17-7).The resistance and reactancecomponents are equal, and form two sides of a right triangle, with the complex imped-anc...

  • Page 334

    Resistance and reactanceSometimes you’ll get data that tells you the resistance and reactance components in acircuit. To calculate the power factor from this, you can either find the phase angle andtake its cosine, or find the absolute-value impedance and take the ratio R/Z.Problem 17-6A circui...

  • Page 335

    Problem 17-8A circuit has 50 Ω of resistance and 30 Ω of inductive reactance in series. A wattmetershows 100 watts, representing the VA power. What is the true power?First, calculate the power factor. You might use either the phase-angle method orthe R/Z method. Suppose you use the phase-angl...

  • Page 336

    Therefore, R717 and X−451.Using the phase-angle method to solve this (the numbers are more manageablethat way than they are with the R/Z method), calculatePhase angle arctan (X/R)arctan (−451/717)arctan (−0.629)−32.2 degreesThen the power factor isPFcos−32.20.84684.6 percentThe VA power...

  • Page 337

    It is undesirable to have power in a transmission line exist in the form of true power.This translates either into heat loss in the line, radiation loss, or both. The place for truepower dissipation is in the load, such as electrical appliances or radio antennas. Anytrue power in a transmission l...

  • Page 338

    An impedance mismatch can usually be corrected by means of matching trans-formers and/or reactances that cancel out any load reactance. This is discussed in thenext chapter.Loss in a mismatched lineWhen a transmission line is terminated in a resistance RZo, then the current and thevoltage are con...

  • Page 339

    This loss occurs at heat dissipation. It is true power. Any true power that goes intoheating up a transmission line is wasted, because it cannot be dissipated in the load.The additional loss caused by standing waves, over and above the perfectly-matchedline loss, is called standing-wave loss.IThe...

  • Page 340

    R0, that is, the resistor is a short circuit, then the circuit is called a series LC circuit,and the impedance at resonance will be extremely low. The circuit will offer practicallyno opposition to the flow of alternating current at the frequency fo. This condition is se-ries resonance.Parallel r...

  • Page 341

    Problem 17-10Find the resonant frequency of a series circuit with an inductance of 100 µH and a ca-pacitance of 100 pF.First, convert the capacitance to microfarads: 100 pF 0.000100 µF. Then find theproduct LC1000.0001000.0100. Take the square root of this, getting 0.100. Fi-nally, divide 0.159...

  • Page 342

    In practical circuits, variable inductors and/or variable capacitors are often placedin tuned circuits, so that small errors in the frequency can be compensated for. Themost common approach is to design the circuit for a frequency slightly higher than fo,and to use a padder capacitor in parallel ...

  • Page 343

    unwieldy. Like crystals, cavities resonate at a fundamental frequency fo, and also at har-monic frequencies.Sections of transmission lineWhen a transmission line is cut to 1/4 wavelength, or to any whole-number multiple ofthis, it behaves as a resonant circuit. The most common length for a transm...

  • Page 344

    A half-wave dipole has a purely resistive impedance of about 70 Ω at resonance.This is like a series-resonant RLC circuit with R70Ω.A half-wave dipole is resonant at all harmonics of its fundamental frequency fo. Thedipole is a full wavelength long at 2fo; it is 3/2 wavelength long at 3fo; it...

  • Page 345

    2. Which of the following is not an example of true power?A. Power that heats a resistor.B. Power radiated from an antenna.C. Power in a capacitor.D. Heat loss in a feed line.3. The apparent power in a circuit is 100 watts, and the imaginary power is 40watts. The true power is:A. 92 watts.B. 100 ...

  • Page 346

    C. Arctan R/X.D. Arctan X/R.9. A wattmeter shows 220 watts of VA power in a circuit. There is a resistance of50Ω in series with a capacitive reactance of −20 Ω. What is the true power?A. 237 watts.B. 204 watts.C. 88.0 watts.D. 81.6 watts.10. A wattmeter shows 57 watts of VA power in a circu...

  • Page 347

    C. 17 MHz.D. 540 kHz.15. A coil and capacitor are in parallel, with L10.0 µH and C10 pF. What is fo?A. 15.9 kHz.B. 5.04 MHz.C. 15.9 MHz.D. 50.4 MHz.16. A series-resonant circuit is to be made for 14.1 MHz. A coil of 13.5 µH isavailable. What size capacitor is needed?A. 0.945 µF.B. 9.45 pF.C. 9...

  • Page 348

    18CHAPTERTransformers andimpedance matchingIN ELECTRICITY AND ELECTRONICS, TRANSFORMERS ARE EMPLOYED IN VARIOUSways . Transformers are used to obtain the right voltage for the operation of a circuit or sys-tem. Transformers can match impedances between a circuit and a load, or between two dif-fer...

  • Page 349

    inductances of the primary and secondary depend on the frequency of operation, andalso on the resistive part of the impedance in the circuit. As the frequency increases,the needed inductance decreases. At high-resistive impedances, more inductance isgenerally needed than at low-resistive impedanc...

  • Page 350

    Epri/Esec Tpri/Tsec117/Esec9/191/Esec9/117Esec117/913 VProblem 18-2A transformer has a primary-to-secondary turns ratio of exactly 1:9. The voltage at theprimary is 117 V. What is the voltage at the secondary?This is a step-up transformer. Plug in numbers again:117/Esec1/9Esec/1179/19Esec91171053...

  • Page 351

    Laminated ironIn transformers for 60-Hz utility ac, and also at low audio frequencies, sheets of siliconsteel, glued together in layers, are often employed as transformer cores. The siliconsteel is sometimes called transformer iron, or simply iron.The reason layering is used, rather than making t...

  • Page 352

    Another winding method is the core method. In this scheme, the primary is placedat the bottom of the E section, and the secondary is placed at the top (Fig. 18-4C). Thecoupling occurs via magnetic flux in the core. The capacitance between the primaryand secondary is much lower with this type of w...

  • Page 353

    The coil windings might be placed one atop the other, or they might be separated(Fig. 18-5) to reduce the capacitance between the primary and secondary.332 Transformers and impedance matching18-5Solenoidal-coretransformer.In a loopstick antenna, the primary serves to pick up the radio signals. Th...

  • Page 354

    halves (Fig. 18-7). You wind the coil inside one of the halves, and then bolt the two to-gether. The final core completely surrounds the loop, and the magnetic flux is confinedto the core material.The autotransformer33318-7Exploded view of pot core (windings not shown).Like the toroid, the pot co...

  • Page 355

    Power transformersAny transformer used in the 60-Hz utility line, intended to provide a certain rms ac volt-age for the operation of electrical circuits, is a power transformer. Power transformersexist in sizes ranging from smaller than a tennis ball to as big as a room.At the generating plantThe...

  • Page 356

    Along the lineExtreme voltage is good for high-tension power transmission, but it’s certainly of nouse to an average consumer. The wiring in a high-tension system must be done usingprecautions to prevent arcing (sparking) and short circuits. Personnel must be kept atleast several feet, or even ...

  • Page 357

    Most solid-state devices use low voltages, ranging from about 5 V up to perhaps 50V. This equipment needs step-down power transformers in its power supplies.Solid-state equipment usually (but not always) consumes relatively little power, so thetransformers are usually not very bulky. The exceptio...

  • Page 358

    Balanced and unbalanced loadsA balanced load is one whose terminals can be reversed without significantly affectingcircuit behavior. A plain resistor is a good example. The two-wire antenna input in atelevision receiver is another example of a balanced load. A balanced transmissionline is usually...

  • Page 359

    balanced and unbalanced parts of the systems are the same, then a 1:1 turns ratio isideal. But if the impedances differ, the turns ratio should be such that the impedancesare matched. This is discussed in the section on impedance transfer ratio that follows.Transformer couplingTransformers are so...

  • Page 360

    The required transformer will have a step-up impedance ratio of Zpri/Zsec50.0/3001:6.00. From the above formulas,Tpri/Tsec(Zpri/Zsec)1/2(1/6.00)1/20.166671/20.40829A couple of extra digits are included (as they show up on the calculator) to preventthe sort of error introduction you recall from ea...

  • Page 361

    air-core coils is that some of the magnetic flux extends outside of the coil. This affectsthe performance of the transformer when it must be placed in a cramped space, such asin a transmitter final-amplifier compartment.A major advantage of coil type transformers, especially when they are wound o...

  • Page 362

    RinZo2/Rout752/1005625/10056ΩProblem 18-6An antenna is known to have a pure resistance of 600 Ω. You want to match it to 50.0 Ωpure resistance. What is the characteristic impedance needed for a quarter-wavematching section?Use this formula:Zo2RinRoutZo26005030,000Zo2(30,000)1/2173ΩThe cha...

  • Page 363

    Reactance makes a perfect match impossible, no matter what the turns ratio or Zoof the transformer. A small amount of reactance can be tolerated at lower radio fre-quencies (below about 30 MHz). A near-perfect match becomes more important athigher frequencies.The behavior of reactance, as it is c...

  • Page 364

    B. 585 V.C. 117 V.D. 2.93 kV.5. A transformer has a secondary-to-primary turns ratio of 0.167. Thistransformer is:A. A step-up unit.B. A step-down unit.C. Neither step-up nor step-down.D. A reversible unit.6. Which of the following is false, concerning air cores versus ferromagnetic cores?A. Air ...

  • Page 365

    11. An advantage of a toroid core over a solenoid core is:A. The toroid works at higher frequencies.B. The toroid confines the magnetic flux.C. The toroid can work for dc as well as for ac.D. It’s easier to wind the turns on a toroid.12. High voltage is used in long-distance power transmission ...

  • Page 366

    C. 1:3.00.D. 1:9.00.18. A quarter-wave matching section has a characteristic impedance of 75.0 Ω. Theinput impedance is 50.0 Ω resistive. What is the resistive output impedance?A. 150 Ω.B. 125 Ω.C. 100 Ω.D. 113 Ω.19. A resistive impedance of 75 Ω must be matched to a resistive imped...

  • Page 367

    Test: Part twoDO NOT REFER TO THE TEXT WHEN TAKING THIS TEST. A GOOD SCORE IS ATleast 37 correct. Answers are in the back of the book. It’s best to have a friend check yourscore the first time, so you won’t memorize the answers if you want to take the testagain.1. A series circuit has a resis...

  • Page 368

    4. A sine wave has a peak value of 30.0 V. Its rms value is:A. 21.2 V.B. 30.0 V.C. 42.4 V.D. 60.0 V.E. 90.0 V.5. Four capacitors are connected in parallel. Their values are 100 pF each. Thenet capacitance is:A. 25 pF.B. 50 pF.C. 100 pF.D. 200 pF.E. 400 pF.6. A transformer has a primary-to-seconda...

  • Page 369

    B. 45 degrees.C. 90 degrees.D. 180 degrees.E. 360 degrees.8. A transmission line carries 3.50 A of ac current and 150 V ac. The true powerin the line is:A. 525 W.B. 42.9 W.C. 1.84 W.D. Meaningless; true power is dissipated, not transmitted.E. Variable, depending on standing wave effects.9. In a p...

  • Page 370

    13. A complex impedance is represented by 34 − j23. The absolute-valueimpedance is:A. 34 Ω.B. 11 Ω.C.23Ω.D. 41 Ω.E. 57 Ω.14. A coil has an inductance of 750 µH. The inductive reactance at 100 kHz is:A. 75.0 Ω.B. 75.0 kΩ.C. 471 Ω.D. 47.1 kΩ.E. 212 Ω.15. Two waves are 180 deg...

  • Page 371

    C. 0.1415 mH.D. 1.64 mH.E. 0.164 mH.19. Which of the following types of capacitor is polarized?A. Mica.B. Paper.C. Electrolytic.D. Air variable.E. Ceramic.20. A toroidal-core coil:A. Has lower inductance than an air-core coil with the same number of turns.B. Is essentially self-shielding.C. Works...

  • Page 372

    B. Reactance isn’t a real physical thing.C. They provide a way to represent what happens in resistance-reactancecircuits.D. Engineers like to work with sophisticated mathematics.E. No! Complex numbers aren’t used to represent impedance.25. Which of the following does not affect the capacitanc...

  • Page 373

    30. The vector 40 + j30 represents:A. 40 Ω resistance and 30 µH inductance.B. 40 uH inductance and 30 Ω resistance.C. 40 Ω resistance and 30 Ω inductive reactance.D. 40 Ω inductive reactance and 30 Ω resistance.E. 40 uH inductive reactance and 30 Ω resistance.31. In a series RC cir...

  • Page 374

    36. The rate of change (derivative) of a sine wave is itself a wave that:A. Is in phase with the original wave.B. Is 180 degrees out of phase with the original wave.C. Leads the original wave by 45 degrees of phase.D. Lags the original wave by 90 degrees of phase.E. Leads the original wave by 90 ...

  • Page 375

    B. XL60Ω and R25Ω.C. XL60 µH and R25Ω.D. C60 µF and R25Ω.E. L60 µH and R25Ω.354 Test: Part twoTEST 2-2Illustration forPART TWO testquestion 41.42. If two sine waves have the same frequency and the same amplitude, but theycancel out, the phase difference is:A. 45 degrees.B. 90 degrees...

  • Page 376

    B. 200 − j200.C. 200 + j100.D. 200 + j200.E. Not determinable from the data given.45. The characteristic impedance of a transmission line:A. Is negative imaginary.B. Is positive imaginary.C. Depends on the frequency.D. Depends on the construction of the line.E. Depends on the length of the line...

  • Page 377

    50. An inductor shows 100 Ω of reactance at 30.0 MHz. What is its inductance?A. 0.531 µH.B. 18.8 mH.C. 531 µH.D. 18.8 µH.E. It can’t be found from the data given.356 Test: Part two

  • Page 378

    3PARTBasic electronics

  • Page 379

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  • Page 380

    19CHAPTERIntroduction tosemiconductorsSINCE THE SIXTIES, WHEN THE TRANSISTOR BECAME COMMON IN CONSUMERdevices, semiconductors have acquired a dominating role in electronics. This chapterexplains what semiconducting materials actually are.You’ve learned about electrical conductors, which pass cu...

  • Page 381

    Nowadays, a transistor about the size of a pencil eraser can perform the functionsof a tube in most situations. Often, the power supply can be a couple of AA cells or a 9-V“transistor battery.”Figure 19-1 is a size comparison drawing between a typical transistor and a typicalvacuum tube.360 I...

  • Page 382

    Gallium arsenide works better than silicon in several ways. It needs less voltage,and will function at higher frequencies because the charge carriers move faster. GaAsdevices are relatively immune to the effects of ionizing radiation such as X rays andgamma rays. GaAs is used in light-emitting di...

  • Page 383

    DopingFor a semiconductor material to have the properties needed to work in electronic com-ponents, impurities are usually added. The impurities cause the material to conductcurrents in certain ways. The addition of an impurity to a semiconductor is called dop-ing. Sometimes the impurity is calle...

  • Page 384

    electron flow all the way back in chapter 1. It would be a good idea to turn back for a mo-ment and review this material, because it will help you understand the concept of hole flow.Hole flowIn a P-type semiconductor, most of the current flows in a way that some people find pe-culiar and esoteri...

  • Page 385

    terminal is connected to the anode (Fig. 19-4A). No current will flow if the battery is re-versed (Fig. 19-4B). The resistor is included in the circuit to prevent destruction of thediode by excessive current.It takes a certain minimum voltage for conduction to occur. This is called the for-ward b...

  • Page 386

    electrons, is made even more deficient. The N-type material constantly feeds electronsto the P-type in an attempt to create an electron balance, and the battery or power sup-ply keeps robbing electrons from the P-type material. This is shown in Fig. 19-5A and isknown as forward bias.When the pola...

  • Page 387

    are pulled towards the positive charge, away from the junction. In the P-type material,holes are pulled toward the negative charge, also away from the junction. The electrons(in the N-type material) and holes (in the P type) are the majority charge carriers. Theybecome depleted in the vicinity of...

  • Page 388

    QuizRefer to the text in this chapter if necessary. A good score is at least 18 correct. Answersare in the back of the book.1. The term “semiconductor” arises from:A. Resistor-like properties of metal oxides.B. Variable conductive properties of some materials.C. The fact that there’s nothin...

  • Page 389

    7. Of the following, which material allows the lowest forward voltage drop in adiode?A. Selenium.B. Silicon.C. Copper.D. Germanium.8. A CMOS integrated circuit:A. Can only work at low frequencies.B. Is susceptible to damage by static.C. Requires considerable power to function.D. Needs very high v...

  • Page 390

    14. When a P-N junction does not conduct, it is:A. Reverse biased.B. Forward biased.C. Biased past the breaker voltage.D. In a state of avalanche effect.15. Holes flow the opposite way from electrons because:A. Charge carriers flow continuously.B. Charge carriers are passed from atom to atom.C. T...

  • Page 391

    20CHAPTERSome uses of diodesTHE TERM DIODE MEANS “TWO ELEMENTS.” IN THE EARLY YEARS OF ELEC-tronics and radio, most diodes were vacuum tubes. The cathode element emitted elec-trons, and the anode picked up electrons. Thus, current would flow as electronsthrough the tube from the cathode to th...

  • Page 392

    is the simplest possible rectifier. That’s its chief advantage over other, more complicatedrectifier circuits. You’ll learn about the different types of rectifier diodes and circuits inthe next chapter.DetectionOne of the earliest diodes, existing even before vacuum tubes, was a semiconductor...

  • Page 393

    The diode in Fig. 20-2 acts to recover the audio from the radio signal. This is calleddetection; the circuit is a detector. If the detector is to be effective, the diode must beof the right type. It should have low capacitance, so that it works as a rectifier at radiofrequencies, passing current ...

  • Page 394

    MixingWhen two waves having different frequencies are combined in a nonlinear circuit, newfrequencies are produced. These new waves are at the sum and difference frequenciesof the original waves. You’ve probably noticed this mixing, also called heterodyning, ifyou’ve ever heard two loud, sine...

  • Page 395

    SwitchingThe ability of diodes to conduct with forward bias, and to insulate with reverse bias,makes them useful for switching in some electronic applications. Diodes can switch atextremely high rates, much faster than any mechanical device.One type of diode, made for use as an RF switch, has a s...

  • Page 396

    is that the diode will always conduct when the forward bias exceeds the breakovervalue. In this case, the voltage across the diode will be constant: 0.3 V for germaniumand 0.6 V for silicon.This property can be used to advantage when it is necessary to limit the amplitudeof a signal, as shown in ...

  • Page 397

    Frequency controlWhen a diode is reverse-biased, there is a region at the P-N junction with dielectricproperties. As you know from the last chapter, this is called the depletion region, be-cause it has a shortage of majority charge carriers. The width of this zone depends onseveral things, includ...

  • Page 398

    Oscillation and amplificationUnder certain conditions, diodes can be made to produce microwave radio signals.There are three types of diodes that do this: Gunn diodes, IMPATT diodes, and tun-nel diodes.Gunn diodesA Gunn diode can produce up to 1 W of RF power output, but more commonly it worksat ...

  • Page 399

    LEDs and IREDsDepending on the exact mixture of semiconductors used in manufacture, visible light ofalmost any color can be produced. Infrared-emitting devices also exist. The most com-mon color for a light-emitting diode (LED) is bright red. An infrared-emitting diode(IRED) produces wavelengths ...

  • Page 400

    A reverse bias is applied to the device. When light falls on the junction, currentflows. The current is proportional to the intensity of the light, within certain limits.Silicon photodiodes are more sensitive at some wavelengths than at others. Thegreatest sensitivity is in the near infrared part...

  • Page 401

    QuizRefer to the text in this chapter if necessary. A good score is at least 18 correct. Answersare in the back of the book.1. When a diode is forward-biased, the anode:A. Is negative relative to the cathode.B. Is positive relative to the cathode.C. Is at the same voltage as the cathode.D. Altern...

  • Page 402

    7. A time-domain display might be found in:A. An ammeter.B. A spectrum analyzer.C. A digital voltmeter.D. An oscilloscope.8. Zener voltage is also known as:A. Forward breakover voltage.B. Peak forward voltage.C. Avalanche voltage.D. Reverse bias.9. The forward breakover voltage of a silicon diode...

  • Page 403

    14. A Gunnplexer can be used as a:A. Communications device.B. Radio detector.C. Rectifier.D. Signal mixer.15. The most likely place you would find an LED would be:A. In a rectifier circuit.B. In a mixer circuit.C. In a digital frequency display.D. In an oscillator circuit.16. Coherent radiation i...

  • Page 404

    21CHAPTERPower suppliesMOST ELECTRONIC EQUIPMENT NEEDS DIRECT CURRENT (DC) TO WORK. BATTER-ies produce dc, but there is a limit to how much energy and how much voltage a bat-tery can provide. The same is true of solar panels.The electricity from the utility company is alternating current (ac) wit...

  • Page 405

    Second, the ac is rectified, so that it becomes pulsating dc with a frequency of ei-ther 60 Hz or 120 Hz. This is almost always done by one or more semiconductor diodes.Third, the pulsating dc is filtered, or smoothed out, so that it becomes a continu-ous voltage having either positive or negativ...

  • Page 406

    A high-quality, rugged power transformer, capable of providing the necessary cur-rents and/or voltages, is crucial in any power supply. The transformer is usually themost expensive component to replace. When designing a power supply, it’s wise tospend a little extra to get a reliable transforme...

  • Page 407

    Diodes can be connected in parallel to increase the current rating. When this isdone, small-value resistors are placed in series with each diode in the set to equalize thecurrent burden among the diodes (Fig. 21-3). Each resistor should have a voltage dropof about 1 V.386 Power supplies21-3When d...

  • Page 408

    maximum expected PIV; therefore, with a half-wave supply, the diodes should be ratedfor at least 4.2 times the rms ac input voltage.Half-wave rectification has some shortcomings. First, the output is hard to smoothout, because the waveform is so irregular. Second, the voltage output tends to drop...

  • Page 409

    The bridge circuit does not need a center-tapped transformer secondary. This is itsmain practical advantage. Electrically, the bridge circuit uses the entire secondary onboth halves of the wave cycle; the center-tap circuit uses one side of the secondary forone half of the cycle, and the other si...

  • Page 410

    a power supply must deliver a high current. Then, the extra diodes—two for each halfof the cycle, rather than one—dissipate more overall heat energy. When current is usedup as heat, it can’t go to the load. Therefore, center-tap circuits are preferable inhigh-current applications.The voltag...

  • Page 411

    This circuit subjects the diodes to a PIV of 2.8 times the rms ac input voltage.Therefore, they should be rated for PIV of at least 4.2 times the rms ac input voltage.In this circuit, each capacitor charges to the peak ac input voltage when there is noload (the output current is zero). As the loa...

  • Page 412

    Capacitors and chokesAnother way to smooth out the dc from a rectifier is to use an extremely large induc-tance in series with the output. This is always done in conjunction with parallel capaci-tance. The inductance, called a filter choke, is on the order of several henrys. If the coilmust carry...

  • Page 413

    If a supply must have a minimum of ripple, two or three capacitor/choke pairsmight be cascaded, or connected one after the other (Fig. 21-11). Each pair is called asection. Multisection filters can consist of either capacitor-input or choke-input sec-tions, but the two types are never mixed.392 P...

  • Page 414

    diode. The voltage drop across a gaseous tube, designed for voltage regulation, is nearlyconstant. Tubes are available for regulation at moderately high voltages.Surge currentAt the instant a power supply is switched on, a sudden current surge occurs, even withno load at the output. This is becau...

  • Page 415

    Transient suppressionThe ac on the utility line is a sine wave with a constant rms voltage near 117 V. But thereare “spikes,” known as transients, lasting microseconds or milliseconds, that attainpeak values of several hundred or even several thousand volts.Transients are caused by sudden cha...

  • Page 416

    it has been installed. If the replacement fuse is rated too high in current, it might notprotect the equipment.Fuses are available in two types: quick-break and slow-blow. You can usually rec-ognize a slow-blow fuse by the spring inside. A quick-break fuse has only a wire or foilstrip. When repla...

  • Page 417

    QuizRefer to the text in this chapter if necessary. A good score is at least 18 correct. Answersare in the back of the book.1. The output of a rectifier is:A. 60-Hz ac.B. Smooth dc.C. Pulsating dc.D. 120-Hz ac.2. Which of the following might not be needed in a power supply?A. The transformer.B. T...

  • Page 418

    7. If a half-wave rectifier is used with 117-V rms ac (house mains), the average dcoutput voltage is about:A. 52.7 V.B. 105 V.C. 117 V.D. 328 V.8. If a full-wave bridge circuit is used with a transformer whose secondaryprovides 50 V rms, the PIV across the diodes is about:A. 50 V.B. 70 V.C. 100 V...

  • Page 419

    B. Use a choke-input filter.C. Connect several chokes in series.D. Use two capacitor/choke sections one after the other.14. Voltage regulation can be accomplished by a Zener diode connected in:A. Parallel with the filter output, forward-biased.B. Parallel with the filter output, reverse-biased.C....

  • Page 420

    20. To service a power supply with which you are not completely familiar, youshould:A. Install bleeder resistors.B. Use proper fusing.C. Leave it alone and have a professional work on it.D. Use a voltage regulator.Quiz399

  • Page 421

    22CHAPTERThe bipolar transistorTHE WORD TRANSISTOR IS A CONTRACTION OF “CURRENT-TRANSFERRING RESIS-tor. “ This is an excellent description of what a bipolar transistor does.Bipolar transistors have two P-N junctions connected together. This is done in ei-ther of two ways: a P-type layer sandw...

  • Page 422

    There are many different kinds of NPN or PNP bipolar transistors. Some are usedfor radio-frequency amplifiers and oscillators; others are intended for audio frequen-cies. Some can handle high power, and others cannot, being made for weak-signal work.Some bipolar transistors are manufactured for t...

  • Page 423

    modeling the behavior of bipolar transistors, so that their operation is easier to understand.A dual-diode NPN transistor model is shown in Fig. 22-3. The base is formed by theconnection of the two diode anodes. The emitter is one of the cathodes, and the collec-tor is the other.402 The bipolar t...

  • Page 424

    voltage. (For silicon, this is about 0.6 V.) But here, the forward bias is zero. Therefore,the emitter-base current, often called simply base current and denoted IB, is zero, andthe emitter-base junction does not conduct. This prevents any current from flowing be-tween the emitter and collector, ...

  • Page 425

    PNP biasingFor a PNP transistor, the situation is just a “mirror image” of the case for an NPN device.The diodes are turned around the opposite way, the arrow points inward rather thanoutward in the transistor symbol, and all the polarities are reversed. The dual-diodePNP model, along with th...

  • Page 426

    If you look at Fig. 22-4 closely, you’ll see that there are some bias values at which atransistor won’t give current amplification. If the E-B junction is not conducting, or ifthe transistor is in saturation, the curve is horizontal. A small change (to the left andright) of the base voltage, ...

  • Page 427

    Dynamic current amplificationAnother way of specifying current amplification is as the ratio of the difference in IC tothe difference in IB. Abbreviate the words “the difference in” by the letter d. Then, ac-cording to this second definition:Current amplification dIC/dIBA graph of collector c...

  • Page 428

    reduced, as shown in Fig. 22-7. Points X and Y in the graph represent the instantaneouscurrent extremes during the signal cycle.Gain versus frequency40722-7Excessive input reducesamplification.When conditions are like those in Fig. 22-7, there will be distortion in a transistoramplifier. The outp...

  • Page 429

    make an amplifier using a transistor at a frequency higher than its fT, you’ll fail! Thus fTrepresents an absolute upper limit of sorts.The alpha cutoff frequency of a transitor is the frequency at which the gain be-comes 0.707 times its value at 1 kHz. A transistor might still have considerab...

  • Page 430

    The bias is set by the ratio of resistances R2 and R3. It can be anything from zero,or ground potential, to + 12 V, the supply voltage. Normally it will be a couple of volts.Capacitors C2 and C3 block dc to or from the input and output circuitry (whateverthat might be) while letting the ac signal...

  • Page 431

    Instead of varying IB by injecting the signal at the base, it’s being done by injectingthe signal at the emitter. Therefore, in the common-base arrangement, the output sig-nal is in phase with the input, rather than out of phase.The signal enters through C1. Resistor R1 keeps the input signal f...

  • Page 432

    The output of this circuit is in phase with the input. The input impedance is high,and the output impedance is low. For this reason, the common-collector circuit can beused to match high impedances to low impedances. When well designed, an emitter fol-lower works over a wide range of frequencies,...

  • Page 433

    B. The collector and emitter leads are interchanged.C. The arrow is pointing inward.D. No! A PNP device cannot be replaced with an NPN.3. A bipolar transistor has:A. Three P-N junctions.B. Three semiconductor layers.C. Two N-type layers around a P-type layer.D. A low avalanche voltage.4. In the d...

  • Page 434

    9. In Fig. 22-12, the forward-breakover point for the E-B junction is nearest to:A. No point on this graph.B. B.C. C.D. D.10. In Fig. 22-12, saturation is nearest to point:A. A.B. B.C. C.D. D.11. In Fig. 22-12, the greatest gain occurs at point:A. A.B. B.C. C.D. D.12. In a common-emitter circuit,...

  • Page 435

    13. The configuration most often used for matching a high input impedance to alow output impedance puts signal ground at:A. The emitter.B. The base.C. The collector.D. Any point; it doesn’t matter.14. The output is in phase with the input in a:A. Common-emitter circuit.B. Common-base circuit.C....

  • Page 436

    C. Avalanche effect.D. Nonlinear output impedance.20. The gain of a transistor in a common-emitter circuit is 100 at a frequency of1000 Hz. The gain is 70.7 at 335 kHz. The gain drops to 1 at 210 MHz. The alphacutoff is:A. 1 kHz.B. 335 kHz.C. 210 MHz.D. None of the above.Quiz415

  • Page 437

    23CHAPTERThe field-effect transistorBIPOLAR TRANSISTORS BEHAVE AS THEY DO BECAUSE CURRENT VARIATIONS AT one P-N junction produce larger current variations at another. You’ve seen a simpli-fied picture of how this happens, and how the effect can be exploited to get currentamplification.The bipol...

  • Page 438

    N-channel versus P-channelA simplified drawing of an N-channel JFET, and its schematic symbol, are shown inFig. 23-1. The N-type material forms the channel, or the path for charge carriers. In theN-channel device, the majority carriers are electrons. The source is at one end of thechannel, and th...

  • Page 439

    In electronic circuits, N-channel and P-channel devices can do the same kinds ofthings. The main difference is the polarity. An N-channel device can almost always bereplaced with a P-channel JFET, and the power-supply polarity reversed, and the cir-cuit will still work if the new device has the r...

  • Page 440

    the depletion region will completely obstruct the flow of charge carriers. This is calledpinchoff, and is illustrated at C.Again, think of the garden-hose analogy. More negative gate voltages, EG, corre-spond to stepping harder and harder on the hose. When pinchoff takes place, you’ve cutoff th...

  • Page 441

    Typical JFET power-supply voltages are comparable to those with bipolar transis-tors. The voltage between the source and drain, abbreviated ED, can range from about3 V to 150 V; most often it is 6 V to 12 V.The biasing arrangement in Fig. 23-4A is commonly used for weak-signal ampli-fiers, low-le...

  • Page 442

    When EG is fairly large and negative, the JFET is pinched off, and no current flowsthrough the channel. As EG gets less negative, the channel opens up, and current be-gins flowing. As EG gets still less negative, the channel gets wider and the current ID in-creases. As EG approaches the point whe...

  • Page 443

    curves is called a family of characteristic curves for the device. The graph of Fig. 23-6shows a family of characteristic curves for a hypothetical N-channel JFET. Engineersmake use of these graphs when deciding on the best JFET type for an electronic circuit.Also of importance is the curve of ID...

  • Page 444

    the drawings of Fig. 23-8. The N-channel device is diffused into a substrate of P-type semi-conductor material. The P-channel device is diffused into a substrate of N-type material.The MOSFET42323-7At A, simplified cross-sectional drawing of an N-channel MOSFET. At B, theschematic symbol.23-8At A...

  • Page 445

    result, the input impedance is even higher than that of a JFET; the gate-to-source re-sistance of a typical MOSFET is comparable to that of a capacitor! This means that aMOSFET draws essentially no current, and therefore no power, from the signal source.Some MOSFETs have input resistance exceedin...

  • Page 446

    Depletion mode versus enhancement modeThe JFET works by varying the width of the channel. Normally the channel is wideopen; as the depletion region gets wider and wider, choking off the channel, the chargecarriers are forced to pass through a narrower and narrower path. This is known as thedeplet...

  • Page 447

    but the device could be an N-channel, depletion-mode MOSFET and the circuit diagramwould be the same. For an N-channel, enhancement-mode device, an extra resistorwould be necessary, running from the gate to the positive power supply terminal. ForP-channel devices, the supply would provide a negat...

  • Page 448

    The dc bias for the common-gate circuit is basically the same as that for the com-mon-source arrangement. But the signal follows a different path. The ac input signal en-ters through C1. Resistor R1 keeps the input from being shorted to ground. Gate bias isprovided by R1 and R2; capacitor C2 plac...

  • Page 449

    causes a fluctuating dc voltage to appear across the resistor. The output is taken fromthe source, and its ac component passes through C1.The output of the common-drain circuit is in phase with the input. This scheme isthe FET analog of the bipolar common-collector arrangement. The output impedan...

  • Page 450

    A note about notationIn electronics, you’ll encounter various different symbols that denote the same things.You might have already noticed that voltage is sometimes abbreviated by the letter E,and sometimes by the letter V. In bipolar and field-effect transistor circuits, you’ll some-times co...

  • Page 451

    5. In a P-channel JFET:A. The drain is forward-biased.B. The gate-source junction is forward biased.C. The drain is negative relative to the source.D. The gate must be at dc ground.6. A JFET is sometimes biased at or beyond pinchoff in:A. A power amplifier.B. A rectifier.C. An oscillator.D. A wea...

  • Page 452

    A. It is easily damaged by static electricity.B. It needs a high input voltage.C. It draws a large amount of current.D. It produces a great deal of electrical noise.13. The input impedance of a MOSFET:A. Is lower than that of a JFET.B. Is lower than that of a bipolar transistor.C. Is between that...

  • Page 453

    19. Which of the following circuits has its output 180 degrees out of phase with itsinput?A. Common source.B. Common gate.C. Common drain.D. All of them.20. Which of the following circuits generally has the greatest gain?A. Common source.B. Common gate.C. Common drain.D. It depends only on bias, ...

  • Page 454

    24CHAPTERAmplifiersIN THE PRECEDING TWO CHAPTERS, YOU SAW SCHEMATIC DIAGRAMS WITH BIPOLARand field-effect transistors. The main intent was to acquaint you with biasing schemes.Some of the diagrams were of basic amplifier circuits. This chapter examines amplifiersmore closely, but the subject is v...

  • Page 455

    For voltageSuppose there is a circuit with an rms ac input voltage of Ein and an rms ac output volt-age of Eout. Then the voltage gain of the circuit, in decibels, is given by the formula:Gain (dB) 20 log10(Eout/Ein)The logarithm function is abbreviated log. The subscript 10 means that the base o...

  • Page 456

    Find the ratio Eout/Ein19.9/24.20.822.... (The three dots indicate extra digitsintroduced by the calculator. You can leave them in untill the final roundoff.) Find thelogarithm of this: log 0.822...0.0849.... Then multiply by 20: Gain 1.699... dB,rounded off to 1.70 dB.Negative gain translates in...

  • Page 457

    Solving this formula proceeds in several steps. First, divide each side by 10, getting1log (Pout/94)Then, take the base-10 antilogarithm, also known as the antilog, of each side.The antilog function is the inverse of the log function; that is, it “undoes” the log func-tion. The function antil...

  • Page 458

    Basic bipolar amplifier circuitIn the previous chapters, you saw some circuits that will work as amplifiers. The princi-ple is the same for all electronic amplification circuits. A signal is applied at some con-trol point, causing a much greater signal to appear at the output.In Fig. 24-2, an NPN...

  • Page 459

    fraction of a microfarad, down to picofarads at the highest frequencies and impedances.The exact values are determined by the design engineers, working to optimize circuit per-formance in the lab.The resistor values likewise depend on the application. Typical values are R1 470Ω, R2 4.7 KΩ, R3...

  • Page 460

    The resistor values depend on the application. In some instances, R1 and C1 are notused, and the source is grounded directly. If R1 is used, its value will depend on the in-put impedance and the bias needed for the FET. Nominal values might be R1 680Ω,R2= 10 KΩ, and R3 100Ω for a weak-signa...

  • Page 461

    voltage) curve. This is shown in Fig. 24-5 for an N-channel device. For P-channel, re-verse the polarity signs.440 Amplifiers24-5Various classes ofamplifier operationfor an N-channelJFET.It is important with class-A amplifiers that the input signal not be too strong. Oth-erwise, during part of th...

  • Page 462

    When a bipolar transistor is biased close to cutoff under no-signal conditions (Fig.24-4), or when an FET is near pinchoff (Fig. 24-5), the input signal will drive the deviceinto the nonlinear part of the operating curve. A small collector or drain current willflow when there is no input, but it ...

  • Page 463

    Class-AB2 and class-B amplifiers take some power from the input signal source. En-gineers say that such amplifiers require a certain amount of drive or driving power tofunction. Class-A and class-AB1 amplifiers theoretically need no driving power, al-though there must be an input voltage.The clas...

  • Page 464

    over 5 dB. Nonetheless, the efficiency is excellent, and class-C operation is common inCW, RTTY, or FM radio transmitters.PA efficiencySaving energy is a noble thing. But in electronic power amplifiers, as with many otherkinds of hardware, energy conservation also translates into lower cost, smal...

  • Page 465

    In class-AB1 or class-AB2, there is low current (and therefore low dc collector ordrain power input) with zero signal, and a higher current (and therefore a higher dcpower input) with signal.In class-B and class-C, there is no current (and therefore zero dc collector or drainpower input) when the...

  • Page 466

    Problem 24-6An FET amplifier is 60 percent efficient. If the power output is 3.5 W, what is the dcdrain power input?“Plug in” values to the formula eff(%) 100 Pout/PD. This gives60100× 3.5/PD60350/PD60/3501/PDPD350/605.8 WEfficiency versus classClass-A amplifiers are the least efficient, in ...

  • Page 467

    In Fig. 24-8B, the output of an overdriven class-B amplifier is shown. The wave isno longer a half sine wave, but instead, it shows evidence of flat topping. The peaks areblunted or truncated. The result of this is audio distortion in the modulation on a radiosignal, and also an excessive amount ...

  • Page 468

    for voice communications must work from 300 Hz to 3 kHz, a 10: 1 span of frequencies.In digital communications, audio amplifiers are designed to work over a narrow range offrequencies, sometimes less than 100 Hz wide.Hi-fi amplifiers are usually equipped with resistor-capacitor (RC) networks that...

  • Page 469

    limits the current through the first transistor, Q1. (In some cases, R1 might be elimi-nated.) Resistors R2 and R3 provide the proper base bias for transistor Q2.The main disadvantage of this scheme is that it costs more than capacitive cou-pling. But transformer coupling can provide an optimum s...

  • Page 470

    In some amplifier systems, capacitors are added across the primary and/or secondaryof the transformer. This results in resonance at a frequency determined by the capaci-tance and the transformer winding inductance. If the set of amplifiers is intended for justone frequency (and this is often the ...

  • Page 471

    Radio-frequency amplificationThe RF spectrum begins at about 9 kHz and extends upward in frequency to well over300 GHz, or 300,000,000,000 Hz. A complete discussion of RF amplifier design wouldoccupy a book. Therefore, again, only a sketch of the most important characteristicscan be given here.We...

  • Page 472

    if this undesired “signal” falls within the design frequency range of the broadband PA, itwill be amplified. The result will be unintended (and illegal!) RF emission from the radiotransmitter. Such unwanted signals are called spurious emissions, and they occur moreoften than you might think.A...

  • Page 473

    A tuned RF PA, providing 3 W output at 10 MHz or so, is shown in Fig. 24-14. Thetransistor is the same as for the broadband amplifier discussed above. The tuning andloading controls should be adjusted for maximum RF power output as indicated on awattmeter in the feed line going to the load.452 Am...

  • Page 474

    QuizRefer to the text in this chapter if necessary. A good score is at least 18 correct. Answersare in the back of the book.1. The decibel is a unit of:A. Relative signal strength.B. Voltage.C. Power.D. Current.2. If a circuit has a voltage-amplification factor of 20, then the voltage gain is:A. ...

  • Page 475

    7. The capacitance values in an amplifier circuit depend on:A. The supply voltage.B. The polarity.C. The signal strength.D. The signal frequency.8. A class-A circuit would not work well as:A. A stereo hi-fi amplifier.B. A television transmitter PA.C. A low-level microphone preamplifier.D. The fir...

  • Page 476

    B. By increasing the drive.C. By using two transistors in push-pull.D. A class-C amplifier cannot be made linear.14. Which of the following amplifier classes generally needs the most drivingpower?A. Class A.B. Class AB1.C. Class AB2.D. Class B.15. A graphic equalizer is a form of:A. Bias control....

  • Page 477

    20. A loading control in a tuned PA:A. Provides an impedance match between the bipolar transistor or FET andthe load.B. Allows broadband operation.C. Adjusts the resonant frequency.D. Controls the input impedance.456 Amplifiers

  • Page 478

    25CHAPTEROscillatorsSOMETIMES AMPLIFIERS WORK TOO WELL. YOU’VE PROBABLY HEARD THIS WHENsomeone was getting ready to speak over a public-address system. The gain was set toohigh. The person began to speak; sound from the speakers got into the microphone,was amplified, went to the speakers again,...

  • Page 479

    Positive feedbackFeedback can be in phase or out of phase. For a circuit to oscillate, the feedback mustbe in phase, or positive. Negative feedback (out of phase) simply reduces the gain.The output of a common-emitter or common-source amplifier is out of phase fromthe input. If you couple the col...

  • Page 480

    The Armstrong oscillatorA common-emitter or common-source amplifier can be made to oscillate by couplingthe output back to the input through a transformer that reverses the phase of thefed-back signal. The phase at a transformer output can be inverted by reversing the sec-ondary terminals.The sch...

  • Page 481

    The circuit uses a single coil with a tap on the windings to provide the feedback. Avariable capacitor in parallel with the coil determines the oscillating frequency, and al-lows for frequency adjustment. This circuit is called a Hartley oscillator.The Hartley oscillator uses about one-quarter of...

  • Page 482

    more than a fraction of a watt of power. If more power is needed, the signal can beboosted by one or more stages of amplification.It’s important to use only the minimum amount of feedback necessary to get oscil-lation. The amount of feedback is controlled by the position of the coil tap.The Col...

  • Page 483

    in place of the drain. The only difference, as you can probably guess by now, is the additionof a resistor between the base and the positive supply voltage (for NPN) or the negative sup-ply voltage (for PNP).The Clapp oscillator offers excellent stability at RF. Its frequency won’t changemuch w...

  • Page 484

    it isn’t hard to get it to oscillate. Another advantage of the Clapp circuit is that it allowsthe use of a variable capacitor for frequency control, while still accomplishing feedbackthrough a capacitive voltage divider.StabilityThe term stability is used often by engineers when they talk about...

  • Page 485

    material. Ferromagnetic solenoidal or toroidal cores aren’t very good for VFO coils, be-cause these materials change their permeability as the temperature varies. This changesthe inductance, in turn affecting the oscillator frequency.Engineers spend much time and effort in finding components th...

  • Page 486

    they are often used as frequency standards, against which other oscillators are cali-brated. The accuracy can be within a few Hertz at working frequencies of several mega-hertz.The voltage-controlled oscillatorThe frequency of a VFO can be adjusted via a varactor diode in the tuned LC circuit. Re...

  • Page 487

    Why control the frequency of an oscillator in this way? It is commonly done in mod-ern communications equipment; there must be a reason. In fact there are several goodreasons why varactor control is better than the use of mechanically variable capacitorsor inductors. But it all comes down to basi...

  • Page 488

    Diode oscillatorsAt ultra-high and microwave frequencies, certain types of diodes can be used as oscil-lators. These diodes, called Gunn, IMPATT, and tunnel diodes, were discussed inchapter 20.Audio waveformsThe above described oscillators work above the human hearing range. At audio fre-quencies...

  • Page 489

    Audio oscillatorsAudio oscillators find uses in doorbells, ambulance sirens, electronic games, and thoselittle toys that play simple musical tunes. All AF oscillators work in the same way, con-sisting of amplifiers with positive feedback.A simple audio oscillatorOne form of AF oscillator that is ...

  • Page 490

    This is sometimes called a multivibrator circuit, although that is technically a mis-nomer, the term being more appropriate to various digital signal-generating circuits.Two N-channel JFETs are connected to form an oscillator as shown in Fig. 25-10.Each “stage” amplifies the signal in class-A...

  • Page 491

    1. Negative feedback in an amplifier:A. Causes oscillation.B. Increases sensitivity.C. Reduces the gain.D. Is used in an Armstrong oscillator.2. Oscillation requires:A. A common-drain or common-collector circuit.B. A stage with gain.C. A tapped coil.D. Negative feedback.3. A Colpitts oscillator c...

  • Page 492

    8. An oscillator might fail to start for any of the following reasons except:A. Low-power-supply voltage.B. Low stage gain.C. In-phase feedback.D. Very low output impedance.9. An advantage of a crystal-controlled oscillator over a VFO is:A. Single-frequency operation.B. Ease of frequency adjustme...

  • Page 493

    15. A ferromagnetic-core coil is preferred for use in the tuned circuit of an RFoscillator:A. That must have the best possible stability.B. That must have high power output.C. That must work at microwave frequencies.D. No! Air-core coils work better in RF oscillators.16. If the load impedance for...

  • Page 494

    20. An IMPATT diode:A. Makes a good audio oscillator.B. Can be used for waveform analysis.C. Is used as a microwave oscillator.D. Allows for frequency adjustment of a VCO.Quiz473

  • Page 495

    26CHAPTERData transmissionTO CONVEY DATA, SOME ASPECT OF A SIGNAL MUST BE VARIED. THERE ARE several different characteristics of a signal that can be made to change in a controlledway, so that data is “imprinted” on it. Modulation is the process of imprinting data ontoan electric current or r...

  • Page 496

    The Morse codeThe simplest, and oldest, form of modulation is on-off keying. Early telegraph systemsused direct currents that were keyed on and off, and were sent along wires. The first ra-dio transmitters employed spark-generated “hash” signals that were keyed using thetelegraph code. The no...

  • Page 497

    teleprinter machines than on-off switching. That is to shift the frequency of the carrierwave back and forth. It is called frequency-shift keying (FSK).Teleprinter codesThe Morse code is not the only digital code of its kind. There are two commonteleprinter codes used to send and receive radiotel...

  • Page 498

    like on-off code keying, is a digital form of communications. But unlike on-off Morsekeying, FSK is frequency modulation (FM).Frequency-shift keying47726-3The Morse code word “eat” as sent using FSK.26-4A simple FSKtransmitter.The telephone modemTeleprinter data can be sent over the telephone...

  • Page 499

    Amplitude modulation for voiceA voice signal is a complex waveform with frequencies mostly in the range 300 Hz to 3kHz. Direct currents can be varied, or modulated, by these waveforms, thereby trans-mitting voice information over wires. This is how early telephones worked.Around 1920, when CW osc...

  • Page 500

    Bandwidth of an AM voice signalSuppose you could get a graphic display of an AM signal, with frequency on the hori-zontal axis and amplitude on the vertical axis. This is in fact done using an instrumentcalled a spectrum analyzer. In Fig. 26-7, the spectral display for an AM voice radiosignal at ...

  • Page 501

    In an AM signal, the bandwidth is twice the highest audio modulating frequency. Inthe example of Fig. 26-7, the voice energy is all below 3 kHz, and the bandwidth of thecomplete RF signal is 6 kHz. At 3 kHz above and below the carrier, the frequency cut-offs are abrupt. This transmitter uses an a...

  • Page 502

    Voice SSBDuring the fifties, engineers began to work on an alternative to conventional AM. Theymused, “Suppose all of the transmitter power could go into the voice, and none betaken up by the carrier? That would be a threefold effective increase in transmitterpower! And what if the bandwidth co...

  • Page 503

    resulting in interference to other stations using the band. Engineers and technicians re-fer to this as splatter.Frequency and phase modulationBoth AM and SSB work by varying the signal strength. This can be a disadvantage whenthere is sferic noise caused by thundershowers in the vicinity. Sferic...

  • Page 504

    this sounds like a “buzz” or “whine.” Sferics and ignition noise are both predominantly am-plitude-modulated.In frequency modulation (FM), the amplitude of the signal remains constant, andthe instantaneous frequency or phase is made to change. Because the carrier is always“full-on,” c...

  • Page 505

    Frequency deviationThe amount by which the carrier frequency varies will depend on the relative audio sig-nal level, and also on the degree to which the audio is amplified before it’s applied to themodulator. The deviation is the maximum extent to which the instantaneous carrierfrequency differ...

  • Page 506

    The ratio of the frequency deviation to the highest modulating audio frequency iscalled the modulation index. For good fidelity, it should be at least 1: 1. But it shouldnot be much more; that would waste spectrum space.Pulse modulationStill another method of modulation works by varying some aspe...

  • Page 507

    Normally, the pulse amplitude increases as the instantaneous modulating-signallevel increases. But this can be reversed, so that higher audio levels cause the pulse am-plitude to go down. Then the signal pulses are at their strongest when there is no mod-ulation.Either the positive or negative PA...

  • Page 508

    number of digital states increases. An example of eight-level PAM/PCM is shown in Fig. 26-12D.Analog-to-digital conversionThe graph of Fig. 26-12D illustrates a method of analog-to-digital (A/D) conversion.A voice signal, or any continuously variable signal, can be digitized, or converted intoa s...

  • Page 509

    A fax signal sounds somewhat like AFSK. But the modulation occurs over a contin-uously variable range of audio tones, rather than at only two frequencies.To send an image by fax, a document or photo is wrapped around a drum. Thedrum is rotated at a slow, controlled rate. A spot of light scans fro...

  • Page 510

    Fast-scan televisionConventional television is also known as fast-scan TV (FSTV). This is the TV that bringsyou sports events, newscasts, and all the other programming with which you’re familiar.In FSTV, the frames come at the rate of 30 per second. The human eye/brain per-ceives bursts of moti...

  • Page 511

    from a distance, the dots are too small to be individually discernible. Various combinationsof red, blue, and green intensities result in reproduction of all possible hues and satura-tions of color.The electromagnetic fieldIn a radio or television transmitting antenna, electrons are moving back a...

  • Page 512

    have exactly the same form. The difference is in their frequency. The frequency of anelectromagnetic wave is directly related to the wavelength in space.Frequency versus wavelengthAll electromagnetic fields have frequencies and wavelengths that are inversely related.If fMHz is the frequency of a ...

  • Page 513

    andfMHz = 300/LmThe electromagnetic spectrumThe whole range of electromagnetic frequencies or wavelengths is called theelectromagnetic spectrum. Theoretically there is no limit to how low or high the fre-quency can be, nor, correspondingly, to how long or short the wavelength can be. Themost comm...

  • Page 514

    Transmission mediaData can be transmitted over various different media. The most common are cable, ra-dio, satellite links, and fiberoptics. Cable, radio/TV, and satellite communications usethe radio-frequency spectrum. Fiberoptics uses infrared or visible light energy.CableThe earliest cables we...

  • Page 515

    Radio amateurs sometimes use parallel-wire transmission lines, resembling the“ribbon” cable popular for use with consumer TV receiving antennas. In a parallel-wireline, the RF currents in the two conductors are always 180 degrees out of phase, so thattheir electromagnetic fields cancel each o...

  • Page 516

    fields. A fiberoptic cable will not corrode as metallic wires do. Fiberoptic cables are in-expensive to maintain and easy to repair. An optical fiber can carry far more signalsthan a cable, because the “carrier” frequency is practically infinite. The whole radiospectrum, from VLF through micr...

  • Page 517

    C. Reduced number of misprints. D. On-off keying is just as good as FSK.4. The maximum AM percentage possible without distortion is:A. 33 percent.B. 67 percent.C. 100 percent.D. 150 percent.5. If an AM signal is modulated with audio having frequencies up to 5 kHz, thenthe complete signal bandwidt...

  • Page 518

    10. A spectrum analyzer displays:A. Time as a function of frequency.B. Frequency as a function of time.C. Signal strength as a function of time.D. Signal strength as a function of frequency.11. The deviation for voice FM signals is usually:A. Plus-or-minus 3 kHz.B. Plus-or-minus 5 kHzC. Plus-or-m...

  • Page 519

    17. The bandwidth of a fax signal is kept narrow by:A. Sending the data at a slow rate of speed.B. Limiting the image resolution.C. Limiting the range of shades sent.D. Using pulse modulation.18. What is the wavelength of a 21.3-MHz signal?A. 46.2 m.B. 14.1 m.C. 21.0 km.D. 6.39 km.19. A coaxial c...

  • Page 520

    27CHAPTERData receptionONCE A SIGNAL HAS LEFT A TRANSMITTER, THE IMPULSES TRAVEL, ORpropagate, in a cable, optical fiber, or space. In cables, the signals are ac (usually) or dc (sometimes). In fiberoptic systems, thesignals are infrared or visible light. The signals are confined in cables and fi...

  • Page 521

    from the transmitting antenna. To some extent, radio waves penetrate nonconductingobjects such as trees and frame houses. The line-of-sight wave consists of two compo-nents: the direct wave and the reflected wave.The direct waveThe longest wavelengths are least affected by obstructions. Atvery lo...

  • Page 522

    The ionosphere consists of three layers, called the D layer, E layer, and F layer. Thelayers form at different altitudes, with the D layer lowest and the F layer highest (Fig.27-2). The D layer absorbs radio waves at frequencies below about 7 MHz. The E and Flayers return radio waves to the earth...

  • Page 523

    Tropospheric EM propagationAt frequencies above about 30 MHz, the lower atmosphere bends radio waves towardsthe surface (Fig. 27-3). Tropospheric banding or tropo occurs because the index ofrefraction of air, with respect to EM waves, decreases with altitude. The effect is simi-lar to sound waves...

  • Page 524

    SensitivityThe sensitivity of a receiver is its ability to recover weak signals and process them intoreadable data. The most common way to express receiver sensitivity is to state the numberof ac signal microvolts at the antenna, needed to produce a given signal-to-noise (S/N)ratio. Sometimes, th...

  • Page 525

    The noise figure (NF) of a receiver is specified in various different ways. Thelower the noise figure, the better the sensitivity. You might see a specification such as“NF: 6 dB or better.”Noise figure depends on the type of active amplifier device used in the front end ofa receiver. Gallium-...

  • Page 526

    enough capacitance so that it follows the carrier frequency. A transistor, biased for class-Boperation, can also be used.The rapid pulsations are smoothed out by passing the output of the diode or tran-sistor through a capacitor of just the right value. The capacitance should be largeenough so th...

  • Page 527

    This demodulation scheme is called heterodyne detection. A receiver that makesuse of a heterodyne detector is called a direct-conversion receiver.Detection of FSK signalsFrequency-shift keying can be detected by using the same methods as CW detection.The carrier beats against the BFO in the mixer...

  • Page 528

    The phase-locked loopIf an FM signal is injected into a phase-locked loop (PLL) circuit, the loop will producean error voltage that is a duplicate of the modulating waveform. The frequency changesmight be too fast for the PLL to lock onto, but the error voltage will still appear. Manymodern recei...

  • Page 529

    negative) is directly proportional to the instantaneous frequency. Therefore, the outputvoltage is a duplicate of the modulating waveform.A discriminator is sensitive to amplitude variations in the signal, but this problemcan be overcome by the use of a limiter.The ratio detectorA discriminator w...

  • Page 530

    weaker or shorter pulses result in decreased amplitude. Because of this, PM can be de-tected in the same way as AM.A major advantage of PM is that it’s “mostly empty space.” With pulse amplitudemodulation (PAM), pulse duration modulation (PDM), or pulse code modulation(PCM), the time interv...

  • Page 531

    You might ask, “Why convert a signal to digital form in the first place, if it’s going tobe changed back to analog form at the receiver anyway?” The reason is that a digital sig-nal is inherently simpler than an analog signal, in the sense that is less random. Thus,a digital signal resemble...

  • Page 532

    number of possible states. The DSP circuit gets rid of confusion between digital states.The result is an output that is essentially free from interference.Digital signal processors are available from several commercial sources. They canbe installed in existing communications receivers.The benefit...

  • Page 533

    A UHF/microwave converterDown conversion is often used to allow reception of ultra-high-frequency (UHF) andmicrowave signals (above 300 MHz). The UHF or microwave input is mixed with an LOto provide an output that falls within the tuning range of a shortwave VHF receiver. Ablock diagram of a down...

  • Page 534

    Product detection is similar to the heterodyne detection in a direct-conversion re-ceiver. But product detection is done at a single frequency, rather than at a variable fre-quency as is the case in direct-conversion reception. The single, constant frequency isobtained by mixing the incoming sign...

  • Page 535

    514 Data reception27-12At A, a passive product detector. At B, a product detector that providessome amplification.

  • Page 536

    The superheterodyneThe superheterodyne uses one or more mixers to convert an incoming signal, re-gardless of its frequency, to an identically modulated signal at some other, constant fre-quency. The signal frequency can be heterodyned once, twice, or even three times.Thus, you might hear of a sin...

  • Page 537

    The IF is easy to process because its frequency never changes. Several IF ampli-fier stages, along with filtering, provide the best possible sensitivity and selectivity. Thispart of the receiver is the IF amplifier chain or IF chain.Image rejectionIn the superhet of Fig. 27-13, the LO frequency, ...

  • Page 538

    Finally, an audio/video amplifier is used to boost the level to whatever is needed todrive the speaker, teleprinter, monitor, or instrumentation at the receiver output.A modulated-light receiverModulated light beams can be demodulated easily using photodiodes or photovoltaiccells, as long as the ...

  • Page 539

    B. Travels just as far as the direct wave.C. Travels farther than the direct wave.D. Might travel less far than, just as far as, or farther than the direct wave.2. The reflected wave:A. Arrives in phase with the direct wave.B. Arrives out of phase with the direct wave.C. Arrives in a variable pha...

  • Page 540

    B. Selectivity.C. Dynamic range.D. Adjacent-channel rejection.9. The ability of a receiver to perform in the presence of strong signals is aconsequence of its:A. Sensitivity.B. Noise figure.C. Dynamic range.D. Adjacent-channel rejection.10. A receiver that responds to a desired signal, but not to...

  • Page 541

    15. Digital modulation is superior to analog modulation in the sense that:A. Analog signals have discrete states, while digital ones vary continuously.B. Digital signals resemble noise less than analog ones.C. Digital signals are easier to use with FM.D. Digital signals have greater bandwidth.16....

  • Page 542

    28CHAPTERIntegrated circuits anddata storage mediaTHE MOST ADVANCED ELECTRONIC CIRCUITS CONTAIN HUNDREDS,thousands, or even millions of diodes, transistors, resistors, and capacitors. This is es-pecially true of industrial and personal computers. These devices use circuits fabri-cated onto wafers...

  • Page 543

    Advantages of IC technologyIntegrated circuits have several advantages over individual, or discrete, components.CompactnessAn obvious asset of IC design is economy of space; ICs are far more compact than equiv-alent circuits made from individual transistors, diodes, capacitors, and resistors.A co...

  • Page 544

    ReliabilityIntegrated circuits fail less often, per component-hour of use, than appliances thatmake use of discrete components. This is mainly a result of the fact that all intercon-nections are sealed within the IC case, preventing corrosion or the intrusion of dust.The reduced failure rate tran...

  • Page 545

    High power necessitates a certain minimum physical bulk, because such amplifiers alwaysgenerate large amounts of heat.This isn’t a serious drawback. Power transistors and vacuum tubes are available toperform high-power tasks. Integrated circuits are no different than anything else:they’re goo...

  • Page 546

    into the inverting input, the output is 180 degrees out of phase with it. An op amp has twopower supply connections, one for the emitters of the transistors (Vee) and one for the col-lectors (Vcc).The symbol for an op amp is a triangle. The inputs, output, and power supply con-nections are drawn ...

  • Page 547

    Open-loop op amps, when used at low frequencies, have extremely high gain, and areprone to instability. They are also usually quite “noisy.”When resistor-capacitor (RC) combinations are used in the feedback loop of anop amp, the amplification changes with frequency. It is possible to get a lo...

  • Page 548

    The analog multiplexerThe analog multiplexer IC allows several different signals to be combined in a singlechannel via time-division multiplexing, in a manner similar to that used with pulse mod-ulation. (This was discussed in chapter 27.) An analog multiplexer can also be used inreverse; then it...

  • Page 549

    528 Integrated circuits and data storage media28-6A simple TTL gate.28-7A simple ECL gate.

  • Page 550

    CMOSComplementary-metal-oxide-semiconductor (CMOS), pronounced “seamoss” (andsometimes written that way by lay people who have heard the term but never seen it indocumentation), employs both N-type and P-type silicon on a single chip. This is anal-ogous to using N-channel and P-channel FETs i...

  • Page 551

    Electronic wristwatches, single-chip calculators, and small microcomputers are ex-amples of devices using LSI ICs. They can be 10 times more sophisticated than MSI de-vices.VLSIVery-large-scale integration (VLSI) devices have from 1,000 to 10,000 componentsper chip. This is an order of magnitude ...

  • Page 552

    A memory that disappears when power is removed is called a volatile memory. Ifmemory is retained when power is removed, it is nonvolatile.ROMBy contrast to RAM, read-only memory (ROM) can be accessed, in whole or in anypart, but not written over. A standard ROM is programmed at the factory. This ...

  • Page 553

    RAM that doesn’t need a backup battery. Another asset is that data can be moved fromplace to place in large chunks. This process is called block memory transfer.IC memory storage capacityIt’s difficult to write about the amount of data that can be stored in an IC memory, sim-ply because the n...

  • Page 554

    Recently, however, compact disks (CDs) have begun to displace magnetic tape for therecording of speech and music.Magnetic tape has millions of iron-oxide or other ferromagnetic particles on a my-lar film. In the recording process, a signal is applied to coils in the recording head. Therecording h...

  • Page 555

    The videocassette recorder (VCR) is used to produce video tapes. These deviceshave become so common that most families today own and use them in the same waythat 8-mm film cameras and projectors were once used. The VCR literally records andplays back a fast-scan television signal.The most common ...

  • Page 556

    returns is reached. Hard disks are permanently installed in the computer. You can’t takeout and replace a hard disk. Complex software—particularly the kind involving graphics,video games and simulations, and complex mathematics—needs a lot of memory space,and as the software itself becomes ...

  • Page 557

    B. Higher power output is possible.C. Higher switching speeds are attainable.D. Fewer calculations need be done in a given time.2. Which of the following is not an advantage of ICs over discrete components?A. Higher component density.B. Ease of maintenance.C. Greater power capability.D. Lower cur...

  • Page 558

    8. Which type of digital IC is least susceptible to noise?A. Transistor-transistor logic.B. Base-coupled logic.C. Emitter-coupled logic.D. N-channel-coupled logic.9. Which of the following is not an advantage of CMOS?A. Relative immunity to noise pulses.B. Low-current requirements.C. Ability to w...

  • Page 559

    15. In magnetic audio tape:A. The tracks are parallel to the edges.B. The tracks are diagonal.C. The tracks are perpendicular to the edges.D. The tracks can be oriented at any angle.16. In magnetic video tape:A. The video tracks are parallel to the edges.B. The video tracks are diagonal.C. The vi...

  • Page 560

    29CHAPTERElectron tubesWHEN YOU THINK OF ELECTRON TUBES, DO YOU IMAGINE THE OLD DAYS OFelectronics? Do you envision radios in racks taller than their operators, with strangelyshaped, glowing, glass globes? Have you heard that “tubes” are totally obsolete?Well, some tubes are still around. The...

  • Page 561

    The diode tubeBefore the start of the twentieth century, scientists knew that electrons could carry acurrent through a vacuum. They also knew that hot electrodes would emit electronsmore easily than cool ones. These phenomena were put to use in the first electrontubes, known as diode tubes, for t...

  • Page 562

    This waiting period can be an annoyance, and it seems bizarre at first to people whohaven’t dealt with tubes before.Cold cathodeIn a gas-filled voltage-regulator tube, the cathode might not have a filament to heat it.Such a device is called a cold-cathode tube. The schematic symbol for a cold-c...

  • Page 563

    A tube with a control grid, in addition to the cathode and plate, is a triode. This isillustrated schematically in Fig. 29-3. In this case, the cathode is indirectly heated; thefilament is not shown. This omission is almost standard in schematics showing tubeswith indirectly heated cathodes. When...

  • Page 564

    bushel basket full of other baseballs. If you throw the ball hard enough, some of theother balls might be jostled out of the basket. Many of these electrons end up “leakingout” through the screen grid, rather than going through the plate circuit of the tube.The result is diminished plate curr...

  • Page 565

    heptode. The usual function of such tubes was signal mixing. The schematic symbol fora hexode is shown at C in Fig. 29-4; the symbol for a heptode is illustrated at D.You’ll probably never hear about these devices in modern electronics, becausesolid-state components are used for signal mixing n...

  • Page 566

    Grounded gridGrounded-cathode RF power amplifiers can (and sometimes do) oscillate, unless theyare neutralized or provided with some negative feedback. The oscillation usually oc-curs at some frequency far removed from the operating frequency. Known as parasiticoscillation, it can rob the amplifi...

  • Page 567

    Cathode-ray tubesEveryone encounters TV picture tubes. You’ve almost certainly looked at a computermonitor (even cash registers have them now), and you’ve probably seen an oscilloscopein some form. These video displays all use cathode-ray tubes (CRTs).The electron beamIn any CRT, an electron ...

  • Page 568

    In an oscilloscope, the horizontal deflecting plates receive a sawtooth voltage wave-form. This causes the beam to scan or sweep at a precise, adjustable speed across thescreen from left to right as seen from the outside. After each timed left- to-right sweep,the beam jumps instantly back to the ...

  • Page 569

    The vidiconVirtually every videocassette recorder (VCR) makes use of a vidicon camera tube.Closed-circuit TV systems, such as the kind you see in convenience stores and banks,also employ the vidicon. The main advantage of the vidicon is its small physical bulk; it’seasy to carry around.In the v...

  • Page 570

    A fine beam of electrons, emitted from the electron gun, scans the target electrode.The secondary electrons cause some of this beam to be reflected back toward the elec-tron gun. Areas of the target electrode with the most secondary-electron emission pro-duce the greatest return beam intensity; r...

  • Page 571

    This is the UHF or microwave signal. The frequency depends mainly on the shape and sizeof the cavities within the magnetron. Small cavities result in the highest oscillation fre-quencies; larger cavities produce oscillation at relatively lower frequencies.A magnetron can generate more than 1 kW o...

  • Page 572

    QuizRefer to the text in this chapter if necessary. A good score is at least 18 correct. Answersare in the back of the book.1. One difference between a triode and an N-channel FET is that:A. Triodes work with lower voltages.B. Triodes are more compact.C. Triodes need more voltage.D. Triodes don...

  • Page 573

    5. In a tube with a directly heated cathode:A. The filament is separate from the cathode.B. The grid is connected to the filament.C. The filament serves as the cathode.D. There is no filament.6. In a tube with a cold cathode:A. The filament is separate from the cathode.B. The grid is connected to...

  • Page 574

    12. The electron gun in a CRT is another name for its:A. Cathode.B. Anode.C. Control grid.D. Screen grid.13. The electron beam in an electrostatic CRT is bent by:A. A magnetic field.B. An electric field.C. A fluctuating current.D. A constant current.14. The horizontal displacement on an oscillosc...

  • Page 575

    B. The longitudinal magnetic flux.C. The bunching-up of the electrons.D. The shapes of the cavities.19. A klystron is noted for its:A. Spiralling electrons.B. Low noise output.C. High achievable output power.D. Magnetic-field intensity.20. In a multicavity klystron, the electrons:A. Have variable...

  • Page 576

    30CHAPTERBasic digital principlesYOU’VE SEEN HOW DIGITAL SIGNALS DIFFER FROM ANALOG SIGNALS. THE MANI-pulation of digital signals is known as digital logic. Digital logic consists of many—sometimes innumerable—pulses racing around. It can be staggering in terms ofquantity, but it is simple ...

  • Page 577

    A decimal number can be represented in digital form, but it requires 10 differentpossible states. Any decimal number has a binary equivalent composed of digits thatare all either 0 or 1: just two different possible states. Much simpler!Modulo what?You probably learned “modular arithmetic” in ...

  • Page 578

    In general, the nth place from the right has the decimal value 2n. The total decimalvalue, for a given binary number, is the sum of the decimal values of each of the places.Converting decimal numbers to binary form can be done using Table 30-1. Sup-pose, for example, that you want to convert 3591...

  • Page 579

    need eight lines. This is called parallel data transfer, because the bits are sent alonglines that are effectively in parallel with each other (Fig. 30-1). Clearly, parallel datatransfer has limitations. For large numbers, it would need many lines. This can presentcertain logistic problems, for e...

  • Page 580

    Positive versus negative logicUsually, logic 1 is high and logic 0 is low. This is known as positive logic. But thesestates can be reversed, and the results will be just as good. When logic 1 is low and logic0 is high (so that a bit 1 is “off” and a bit 0 is “on”), negative logic isbeing ...

  • Page 581

    low. This operation gets its name from the fact that it corresponds to the function of theword “and” in propositional calculus. It is usually represented as multiplication. SeeTable 30-3.ORThe logic OR, or disjunction, also involves two variables. The resultant is high if eitherof the variabl...

  • Page 582

    Symbols for logic gatesA logic gate is an electronic switch that performs a logic operation. The earliest logicgates were built using vacuum tubes; later, transistors and diodes were employed. Mod-ern logic gates are fabricated on integrated circuits (ICs), with hundreds or even thou-sands of gat...

  • Page 583

    Suppose you want to find an arrangement of logic gates for some complex logic op-eration. This can be done in two ways. You can use either truth tables or Boolean al-gebra. For any complex logic operation, there might be several solutions, somerequiring more gates than others. A digital design en...

  • Page 584

    There are three variables X, Y, and Z. Each can be either 0 or 1 (low or high). All thepossible combinations are listed by writing binary numbers XYZ upwards from 000through 111. This forms the first column of the truth table. If there are n total variables,there will be 2n possible combinations....

  • Page 585

    Boolean algebraUsing Boolean representations for logic operations, some of the mathematical proper-ties of multiplication, addition, and negation can be applied to form Boolean equations.The logical combinations on either side of any equation are equivalent.In some ways, Boolean algebra differs f...

  • Page 586

    A flip-flop is a form of sequential logic gate. In a sequential gate, the output statedepends on both the inputs and the outputs. The term “sequential” comes from the factthat the output depends not only on the current states, but on the states immediatelypreceding. A flip-flop has two states...

  • Page 587

    SynchronousAn R-S flip-flop output changes state as soon as the inputs change. If the inputs changeat irregular intervals, so will the outputs. For this reason, the aforementioned circuit issometimes called an asynchronous flip-flop.A synchronous flip-flop changes state only at certain times. The...

  • Page 588

    changes state after every n input pulses, the output frequency is 1/n of the input fre-quency. Counters are built up by interconnecting many flip-flops.A special type of counter can be instructed to divide by any desired positive inte-ger n. This is a programmable divider. It forms the heart of a...

  • Page 589

    The digital revolutionThis chapter has touched upon digital basics, but cannot possibly go into depth. Thescope of digital electronics is vast, and it grows and changes daily. If you are studying tobe an electrical engineer, you’ll take numerous courses in digital electronics.Specialties includ...

  • Page 590

    5. Which of the following voltages could normally represent a 1 in positive logic?A. 0 V.B.1 V.C.4 V.D.12 V.6. Which of the following voltages might normally represent a 1 in negative logic?A. 0 V.B.4 V.C.6 V.D.12 V.7. If X is low, what is the state of X AND Y?A. There is not enough information t...

  • Page 591

    12. Data sent along a single line, one bit after another, is called:A. Serial.B. Synchronous.C. Parallel.D. Asynchronous.13. If X 1 and Y 1, then X YZ is:A. Always 0.B. 0 if Z 0, and 1 if Z 1.C. 1 if Z 0, and 0 if Z 1.D. Always 1.14. If X 0 and Y 1, then X(Y + Z) is:A. Always 0.B. 0 if Z 0, and 1...

  • Page 592

    19. When both inputs of an R-S flip-flop are 1:A. The outputs stay as they are.B. Q 0 and Q1.C. Q 1 and Q 0.D. The resulting outputs can be absurd.20. A frequency synthesizer makes use ofA. An OR gate.B. A divider.C. The octal numbering system.D. The hexadecimal numbering system.Quiz571

  • Page 593

    Test: Part ThreeDo not refer to the text when taking this test.1. In a junction FET, the control electrode is usually the:A. Source.B. Emitter.C. Drain.D. Base.E. Gate.2. A diode can be used as a frequency multiplier because of its:A. Junction capacitance.B. Nonlinearity.C. Avalanche voltage.D. F...

  • Page 594

    5. Which of the following is not characteristic of an oscillator?A. Negative feedback.B. Good output-to-input coupling.C. Reasonably high transistor gain.D. Ac output.E. Usefulness as a signal generator.6. Which layer of the ionosphere absorbs radio signals below about 7 MHz duringthe daylight ho...

  • Page 595

    11. When the bias in an FET stops the flow of current, the condition is called:A. Forward breakover.B. Cutoff.C. Reverse bias.D. Pinchoff.E. Avalanche.12. A vacuum tube would most likely be found in:A. The front end of a radio receiver.B. A high-power radio-frequency linear amplifier.C. A low-lev...

  • Page 596

    17. When both N-channel and P-channel transistors are found in a metal-oxide-semiconductor-type integrated circuit, the technology is known as:A. Transistor-transistor logic.B. CMOS.C. Bipolar logic.D. NPNP.E. PNPN.18. A common-base circuit is commonly employed as:A. A microwave oscillator.B. A l...

  • Page 597

    23. If the source-gate junction in an FET conducts:A. It is a sign of improper bias.B. The device will work in class C.C. The device will oscillate.D. The device will work in class A.E. The circuit will have good stability.24. The octal number system uses modulo:A. 2.B. 8.C. 10.D. 12.E. 16.25. Si...

  • Page 598

    D. A resistor in series and an inductor in parallel with the dc output.E. A capacitor in parallel with the dc output.29. Which of the following bipolar-transistor circuits can, in theory, provide themost amplification?A. Common emitter.B. Common base.C. Common collector.D. Common gate.E. Common d...

  • Page 599

    B. SSB.C. FM.D. RTTY.E. PCM.35. A type of electron tube that can be used to generate microwave energy is:A. A triode.B. An oscillotron.C. A cathode-ray tube.D. A videotron.E. A magnetron.36. In an AND gate, the output is high:A. If any input is high.B. Only when all inputs are low.C. If any input...

  • Page 600

    A. If any input is high.B. Only when all inputs are low.C. If any input is low.D. Only when all inputs are high.E. Only when the inputs have opposite logic states.41. A ratio detector is a circuit for demodulating:A. AM.B. PM.C. FM.D. SSB.E. AFSK.42. In a radio-frequency power amplifier using a v...

  • Page 601

    E. Broadcast transmitter power amplifiers.46. An optoisolator consists of:A. Two Zener diodes back to back.B. An LED and a photodiode.C. Two NPN transistors in series.D. An NPN transistor followed by a PNP transistor.E. A PNP transistor followed by an NPN transistor.47. When a semiconductor is re...

  • Page 602

    4Part Advancedelectronicsand related technology

  • Page 603

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  • Page 604

    31CHAPTERAcoustics, audio, andhigh fidelityUP TO THIS POINT, WE HAVE STUDIED COMPONENTS, CIRCUITS, AND SYSTEMS INwhich esthetic appeal is not especially important. When you are stranded in a snow-storm and you switch on the cell phone to call for help, you probably won’t care whatthe phone set ...

  • Page 605

    In music, audio frequencies are divided into three broad, vaguely defined parts,called bass (pronounced “base”), midrange, and treble. The bass frequencies start at 20Hz and extend to 150 or 200 Hz. Midrange begins at this point, and extends to 2000 or3000 Hz. Treble consists of the audio fre...

  • Page 606

    sound systems and concert halls. The goal is to make sure that all the instrumentssound realistic everywhere in the room.Suppose you have a sound system set up in your living room. You sit on the couchand listen to music. Imagine that, for the particular placement of speakers with respectto your ...

  • Page 607

    sense sound levels according to the logarithm of the actual intensity. Another vari-able in the transmission of sound is the phase with which waves arrive at your ears.This allows you to tell from which direction a sound is coming, and it can producedramatic variations in perceived sound volume a...

  • Page 608

    If the listener moves a few feet, the antinodes will no longer be observed at 700 Hzand its harmonics. The frequency might change; the effect might diminish or even seemto disappear altogether. As produced by the set of baffles, the antinode for 700 Hz andits harmonics might well be confined to a...

  • Page 609

    distortion meters, excessive input will cause the needles to kick into the red range ofthe scale during peaks. If the input is driven up still more, the needle will stay in the redrange much of the time. Some people might say it’s “cool” to run a hi-fi amplifier thisway. If lousy sound is w...

  • Page 610

    amplification stages. In tape recording, there is also some tape hiss. A scheme calledDolby (a trademark of Dolby Laboratories) is used in professional recording studios,and also in high-end consumer tape equipment, to minimize this hiss. Digital recordingtechniques, such as is used in compact di...

  • Page 611

    MHz). Tuners don’t have built-in amplifiers. Although they can provide enoughpower to drive a headset, an amplifier must usually be added if you want to usespeakers.Modern hi-fi tuners are synthesized, deriving their frequency from a quartz crystaland phase-locking circuits. When a station is r...

  • Page 612

    be received clearly. Commercially manufactured tuners often have CD and tape players built in.The amplifierIn hi-fi, an amplifier is usually a self-contained box that delivers medium or high au-dio power to a set of speakers. There is at least one input, but more often there areseveral: one for a...

  • Page 613

    seen in home entertainment systems, especially those used by children and youngadults who have visions of becoming popular-music icons.Balance controlIn hi-fi stereo sound equipment, the balance control allows adjustment of the rela-tive volumes of the left and right channels.In simple hi-fi rece...

  • Page 614

    volume decreases. When the knob is rotated clockwise, the right-channel volume in-creases and the left-channel volume decreases.In sophisticated sound systems, the balance is adjusted via two volume controls,one for the left channel and the other for the right channel. The most advanced soundsyst...

  • Page 615

    together, the impedances are connected in parallel. This will cause impedance mis-matches for most or all of the sources, as well as at the amplifier input. The result willbe degradation of system efficiency and poor overall performance.Another problem is that the signal amplitudes from various s...

  • Page 616

    Sophisticated mixers have exotic features, such as echo effects, frequency-re-sponse filters, and multiple graphic equalizers. Some mixers have an automatic levelcontrol (ALC) that can be switched in to prevent exceptionally loud sound peaks fromcausing distortion. Some units have VU meters for e...

  • Page 617

    and 2.5, 7, and 18 kHz. (These are not standard frequencies; they are given here onlyfor illustrative purposes.) The slide potentiometers are shown as variable resistors fol-lowing the attenuators. Finally, the signals pass through an audio combiner (mixer); thecomposite is sent to the output.The...

  • Page 618

    contained within the headset. There are portable cassette tape players and CD playersthat allow private hi-fi listening via headsets. The sound quality from these systems canbe excellent. The most important factor is the quality of the headset.A headphone radio should never be worn while driving ...

  • Page 619

    Vinyl diskVinyl disks require a turntable that spins at speeds of 33 and 45 revolutions perminute (rpm). There are various drive systems. These are called rim drive, beltdrive, and direct drive. The best type is a matter of individual taste because thereare various factors to consider, such as co...

  • Page 620

    Digital sound, recorded on the surface of a compact disk, is practically devoid of thehiss and crackle that have historically bedeviled recordings on other media. This is be-cause the information on the disk is binary: a bit (binary digit) is either 1 (high) or 0(low). The distinction between the...

  • Page 621

    supply reel is usually on the left, and the take-up reel is on the right. The reels rotatecounterclockwise as the tape passes through the recording/playback mechanism. Whenthe take-up reel is full and the supply reel is empty, both reels can be flipped over andinterchanged. This allows recording ...

  • Page 622

    the recording head when the audio was originally recorded on the tape. This magneticfield induces weak alternating currents in the playback head. These currents are ampli-fied and delivered to a speaker, headset, or other output device.Digital audio tapeDigital audio tape (DAT) is magnetic record...

  • Page 623

    If you have an amateur or citizens’ band (CB) radio station in your house and itcauses EMI to your hi-fi system, two more steps might be necessary:• Locate the radio transmitting antenna as far from the hi-fi equipment aspossible.• Use the lowest possible transmitter output power that will ...

  • Page 624

    C. A tenfold increase in acoustic power.D. No change in acoustic power.6. A sound whose wavelength is 6 in in the air has a frequency of:A. 550 Hz.B. 1100 Hz.C. 2200 Hz.D. It is impossible to calculate from this information.7. A sound wave that travels at 335 m per second has a frequency of:A. 33...

  • Page 625

    C. Electromagnetic interference is likely to occur.D. The speakers are likely to produce distortion of the sound.13. Which of the following frequencies cannot be received by an AM/FM tuner?A. 830 kHz.B. 95.7 kHz.C. 100.1 MHz.D. 107.3 MHz.14. A woofer:A. Is especially useful for reproducing the so...

  • Page 626

    19. Which of the following media or devices use digital-to-analog conversion?A. A CD player.B. A speaker.C. A microphone.D. A vinyl disk.20. Phase quadrature is sometimes used to:A. Increase the output from a microphone.B. Reduce the susceptibility of a hi-fi system to EMI.C. Create the illusion ...

  • Page 627

    32CHAPTERWireless and personalcommunications systemsTHE TERM WIRELESS WAS COINED IN THE LATE NINETEENTH CENTURY WHENinventors toyed with the idea of sending and receiving telegraph messages using elec-tromagnetic fields rather than electric currents. In the early twentieth century, thetechnology ...

  • Page 628

    In an ideal cellular network, all the transceivers are always within range of at leastone repeater. The repeaters pick up the transmissions from the portable units and re-transmit the signals to the telephone network and to other portable units. The region ofcoverage for any repeater (also known ...

  • Page 629

    mind that your conversations are not necessarily private. It is easier for unautho-rized people to eavesdrop on wireless communications than to intercept wire or ca-ble communications.Cell phones and computersA personal computer (PC) can be hooked up to the telephone lines for use with on-line ne...

  • Page 630

    are much larger in a satellite network than in a cellular network, and they change insize and shape if the satellite moves relative to the earth’s surface.Geostationary-orbit satellitesFor any satellite in a circular orbit around the earth, the revolution period getslonger as the altitude incre...

  • Page 631

    longer. This doesn’t cause problems in television broadcasting or in one-way data trans-fers, but it slows things down when computers are linked with the intention of combin-ing their processing power. It is also noticeable in telephone conversations.Problem 32-1What is the minimum round-trip s...

  • Page 632

    “birds” are called medium-earth-orbit (MEO) satellites. A MEO satellite takesseveral hours to complete each orbit. MEO satellites operate in fleets, in a mannersimilar to the way LEO satellites are deployed. Because the average MEO altitudeis higher than the average LEO altitude, each “bird...

  • Page 633

    Acoustic transducersAn acoustic transducer is an electronic component that converts sound waves intosome other form of energy, or vice versa. The other form of energy is usually an al-ternating-current (ac) electrical signal. The waveforms of the acoustical and electri-cal signals are identical, ...

  • Page 634

    capacitance fluctuates, the plates alternately charge and discharge a little. This causesa weak ac signal to be produced, whose waveform is similar to that of the acoustic dis-turbance. The blocking capacitor allows this ac signal to pass to the transducer output,while keeping the dc confined to ...

  • Page 635

    range from about 9 kHz to several hundred gigahertz, into ac signals that are amplifiedby the receiving apparatus. A transmitting antenna converts powerful alternating cur-rents into EM fields, which propagate through space.There are a few significant differences between receiving antennas and tr...

  • Page 636

    of the rays emitted by the semiconductor junction. The modulation contains informa-tion, such as which channel your television set should seek, or whether the volume is tobe raised or lowered. Infrared energy is not visible, but at some wavelengths it can befocused by ordinary optical lenses and ...

  • Page 637

    directly without the data having to pass through any intermediary. This offers greater privacy and individuality than the client-server topology, but it is slower when a largenumber of users need to share data.In the illustrations, only three PCs are shown in the networks. But any LAN canhave as ...

  • Page 638

    car. If a potential thief knows your vehicle has a wireless security system, he or shewill probably not want to spend a lot of time snooping around to find and disable the system.If someone manages to steal your car and it has a wireless security system in-stalled, and if you’re lucky enough to...

  • Page 639

    computer or hi-fi stereo system. Accessories can be added until a ham “rig” is a largeinstallation, comparable to a small commercial broadcast station.Figure 32-8 shows an example of a fixed, computer-controlled amateur radio sta-tion. The PC can be used to communicate via packet radio with o...

  • Page 640

    wavelengths of most broadcast and communications signals, which had wavelengthsin the kilometer range.Anyone can build or obtain a shortwave or general-coverage radio receiver, installa modest outdoor antenna, and listen to signals from all around the world. This hobbyis called shortwave listenin...

  • Page 641

    Minimizing noiseThe noise level in any electronic system can be minimized by using components thatdraw the least possible current. Noise can also be kept down by lowering the tem-perature tremendously. Some experimentation has been done at extremely coldtemperatures; this is called cryotechnology...

  • Page 642

    B. A local-area network.C. A client-server network.D. A peer-to-peer network.2. Infrared and optical wireless links work best:A. Over distances exceeding 1000 miles.B. On a line of sight.C. At low radio frequencies.D. In situations with high levels of noise.3. Which of the following devices or sy...

  • Page 643

    B. 100 millimeters to 1 meter.C. 1 to 10 meters.D. 10 to 100 meters.9. In general, as the noise level in a wireless system increases:A. Stronger incoming signals are needed to overcome it.B. Weaker signals can be received.C. The temperature of the system rises.D. The bandwidth of the system incre...

  • Page 644

    15. An electromagnetic wave can be considered to fall in the shortwave band if itsfree-space wavelength is:A. 55 kilometers.B. 55 meters.C. 55 centimeters.D. 55 millimeters.16. In a cellular network, a base station is sometimes called a:A. Transceiver.B. Cell.C. Repeater.D. Cell phone.17. An adva...

  • Page 645

    62433CHAPTERComputers andthe InternetDURING THE 1980S, PERSONAL COMPUTING BOOMED INTO A HOBBY. BY THEmid-1990s, these machines, which had been esoteric to most people only a generationbefore, were common electronic appliances in households, businesses, and governmentagencies at all levels. Comput...

  • Page 646

    same chip as the microprocessor, but they are often separate. The external chipscontain memory and programming instructions.You might think of the microprocessor as the computer’s conscious mind, which di-rects the behavior of the machine by deliberate control. The CPU, dominated by the mi-crop...

  • Page 647

    Bytes, kilobytes, megabytes, and gigabytesA byte is a unit of digital data, consisting of a string of eight bits. One byte constitutesroughly the same amount of data as one character, such as a letter, numeral, punc-tuation mark, space, or line-feed/return command.Today’s computers work with fi...

  • Page 648

    the data is located or is to be written. Then the head must stabilize its position and gen-erate or detect the magnetic fields. All this takes place in a small fraction of a second.Data arrangement and capacityThe data on a hard drive is arranged in circular tracks. This is not quite like the spi...

  • Page 649

    number of arcs called sectors. A cylinder is the set of equal-radius tracks on all theplatters in the drive. Tracks and sectors are set up on the hard drive during the ini-tial formatting process. There are also data units called clusters. These are unitsconsisting of one to several sectors, depe...

  • Page 650

    Zip disks can hold about 100 MB of data; newer ones can hold 250 MB. Jaz disks holdabout 1 GB. There are several variants on the Zip/Jaz theme, produced by various man-ufacturers. All these disk types require special drives. Some new computers includebuilt-in Zip drives.A popular mass-storage med...

  • Page 651

    changes you have made) to unused space on the disk; the old data (as it was before youopened the file) stays in its old location. This is a safeguard, in case you decide to undothe changes you made.All the data passing between the disks and the memory, and between the memoryand the CPU, is in mac...

  • Page 652

    “chip.” Other factors, such as microprocessor speed, have a practical effect on theusable memory capacity. A gigantic memory will not be of much use if the micro-processor is slow. Nor will a fast microprocessor be of practical value if the memorycapacity is too small for applications that de...

  • Page 653

    (mm), of the individual elements in the display—the “smallest unbreakable pieces.”A good display has a dot pitch that is a small fraction of a millimeter. A typical CRThas a dot pitch of 0.25 or 0.26 mm. The smaller the number, the higher the resolutionand, all other factors being equal, th...

  • Page 654

    yellow, green, blue, indigo, violet). Saturation is the “richness” of color; the higher thesaturation, the more intense a given hue appears. The “techies” use numbers from180 to 180 to represent hue, and from 0 to 100 to represent saturation. Another wayto specify color is according to th...

  • Page 655

    who use portable computers, because these printers are physically small and light. Asimple gray-scale thermal printer employs special paper that darkens when it gets hot.The print mechanism works something like that of a dot-matrix printer. But instead ofthe print head pressing ink onto the page,...

  • Page 656

    The laser blinks rapidly while it scans a cylindrical drum. The drum has specialproperties that cause it to attract the printing chemical, called toner, in some places butnot others, creating an image pattern that will ultimately appear on the paper. A sheetof paper is pulled past the drum and al...

  • Page 657

    alternation between the two tones. In modulation, digital data is changed into ana-log data. It is a type of digital-to-analog (D/A) conversion. Demodulation changesthe analog signals back to digital ones; this is analog-to-digital (A/D) conversion.If you happen to pick up a telephone extension w...

  • Page 658

    machines “speak the same language.” The modern Internet is such that you can useany type of computer—IBM-compatible, Mac, or other—and take advantage of allthe network’s resources.All Internet activity consists of computers “talking” to one another. This occurs inmachine language. H...

  • Page 659

    cannot be completely reconstructed until all the packets have arrived and the destina-tion computer has ensured that there are no errors.E-mail and newsgroupsFor many computer users, communication via Internet electronic mail (e-mail)and/or newsgroups has practically replaced the postal service. ...

  • Page 660

    To effectively use e-mail or newsgroups, everyone must have an Internet address.These tend to be arcane. An example issciencewriter@nanosecond.comThe first part of the address, before the @ symbol, is the username. The word afterthe @ sign and before the period (or dot) represents the domain name...

  • Page 661

    You must take time differences into account if you’re not in the same time zone asthe remote computer.The World Wide Web (also called WWW or the Web) is one of the most powerfulinformation servers you will find on-line. Its outstanding feature is hypertext, a schemeof cross-referencing. Certain...

  • Page 662

    3. Image resolution can be specified in terms of:A. Megahertz.B. Color intensity.C. Wavelength.D. Dot pitch.4. A cluster is a unit of:A. Frequency on a hard drive.B. Data on the Internet.C. Data on a hard drive.D. Bandwidth on the Internet.5. An example of a mass-storage device is a:A. Hard drive...

  • Page 663

    10. A packet is:A. A computer memory module.B. A unit of 210 bytes.C. A piece of a file sent over the Net.D. A picture element in a computer monitor.11. A motherboard contains:A. A microprocessor.B. An external modem.C. A diskette drive.D. A display screen.12. Cross-referencing among web pages is...

  • Page 664

    17. Which of the following is a serial-access medium?A. Computer memory.B. Magnetic tape.C. A hard drive.D. CD-ROM.18. When computer data is sent over long-distance telephone circuits, the digitalhighs and lows are generally represented by:A. Audio tones.B. A series of clicks.C. Positive and nega...

  • Page 665

    34CHAPTERRobotics andartificial intelligenceA ROBOT IS A SOPHISTICATED MACHINE, OR A SET OF MACHINES WORKING together, that performs certain tasks. Some people imagine robots as having two legs, ahead, two arms with functional end effectors (hands), an artificial voice, and an elec-tronic brain. ...

  • Page 666

    These rules were first coined in the 1940s, but they are still considered good stan-dards for robots nowadays.Robot generationsSome researchers have analyzed the evolution of robots, marking progress accord-ing to so-called robot generations. This has been done with computers and inte-grated circ...

  • Page 667

    There are some situations in which autonomous robots don’t work well. In thesecases, many simple robots, all under the control of one central computer, can be used.They function like ants in an anthill or bees in a hive. The individual machines are stu-pid, but the group as a whole is intellige...

  • Page 668

    disease. Controlled by a central microprocessor, they could seek out the disease bacte-ria or viruses and swallow them up.Autonomous robotsA robot is autonomous if it is self-contained, housing its own computer system, andnot depending on a central computer for its commands. It gets around under ...

  • Page 669

    puter communicates with, and coordinates, the robots through wires or fiber optics orvia radio. In the drawing at B, each robot has its own controller, and there is no centralcomputer. Straight lines show possible paths of communication among robot con-trollers in both scenarios.Simple robots, li...

  • Page 670

    You can use your own arm to get an idea of the degrees of freedom that a robot armmight have. Extend your right arm straight out toward the horizon. Extend your indexfinger so it is pointing. Keep your arm straight, and move it from the shoulder. You canmove in three ways. Up-and-down movement is...

  • Page 671

    have three degrees of freedom: base rotation (the equivalent of azimuth), elevationangle, and reach (the equivalent of radius). If you’re a mathematician, you might rec-ognize this as a spherical coordinate scheme. There are several different articulatedgeometries for any given number of degree...

  • Page 672

    Cylindrical coordinate geometryA robot arm can be guided by means of a plane polar coordinate system with an ele-vation dimension added (Fig. 34-4). This is known as cylindrical coordinate geom-etry. In the cylindrical system, a reference plane is used. An origin point is chosen inthis plane. A r...

  • Page 673

    bled back on itself. There might be, but is not always, a wrist joint that can flex likethe elbow and/or twist around and around.A 90-degree-elevation revolute robot arm can reach any point within a half sphere.The radius of the half sphere is the length of the arm when its elbow and wrist (if an...

  • Page 674

    Binaural hearingEven with your eyes closed, you can usually tell from which direction a sound is com-ing. This is because you have binaural hearing. Sound arrives at your left ear witha different intensity, and in a different phase, than it arrives at your right ear. Yourbrain processes this info...

  • Page 675

    Hearing and AIWith the advent of microprocessors that can compare patterns, waveforms, andhuge arrays of numbers in a matter of microseconds, it is possible for a robot to de-termine the nature of a sound source, as well as where it comes from. A human voiceproduces one sort of waveform, a clarin...

  • Page 676

    a robot to determine subtle things like this from the images it sees? It is important for apolice robot or a security robot to know what constitutes a threat and what does not.In some robot applications, it isn’t necessary for the robot to know much aboutwhat’s happening. Simple object recogn...

  • Page 677

    or a UV device. Or the robot might emanate radio waves and detect the echoes; this isradar. Some robots can navigate via ultrasonic echoes, like bats; this is sonar.Binocular visionBinocular machine vision is the analog of binocular human vision. It is sometimescalled stereo vision.In humans, bin...

  • Page 678

    These are the three primary colors. All possible hues, levels of brightness, and levels ofsaturation are made up of these three colors in various ratios. The signals from the threecameras are processed by a microcomputer, and the result is fed to the robot controller.Robotic navigationMobile robo...

  • Page 679

    Edge detectionThe term edge detection refers to the ability of a robotic vision system to locateboundaries. It also refers to the robot’s knowledge of what to do with respect tothose boundaries.A robot car, bus, or truck might use edge detection to see the edges of a road anduse the data to kee...

  • Page 680

    Embedded pathAn embedded path is a means of guiding a robot along a specific route. This schemeis commonly used by a mobile robot called an automated guided vehicle (AGV). Acommon embedded path consists of a buried, current-carrying wire. The current inthe wire produces a magnetic field that the ...

  • Page 681

    Epipolar navigationEpipolar navigation is a means by which a machine can locate objects in three-di-mensional space. It can also navigate, and figure out its own position and path.Epipolar navigation works by evaluating the way an image changes as the viewermoves. The human eyes and brain do this...

  • Page 682

    era, and AI software. You can figure out your coordinates and altitude, using onlythese devices, by letting the computer work with the image of the island. As you flyalong, you aim the camera at the island and keep it there. The computer sees an im-age that constantly changes shape. The computer ...

  • Page 683

    ApplicationsYou can certainly think of many different uses for a telepresence system. Some ap-plications are• Working in extreme heat or cold• Working under high pressure, such as on the sea floor• Working in a vacuum, such as in space• Working where there is dangerous radiation• Disarm...

  • Page 684

    LimitationsIn theory, the technology for telepresence exists right now. But there are some prob-lems that will be difficult, if not impossible, to overcome.The most serious limitation is the fact that telemetry cannot, and never will, travelfaster than the speed of light in free space. This seems...

  • Page 685

    Expert systemsThe term expert systems refers to a method of reasoning in AI. Sometimes thisscheme is called the rule-based system. Expert systems are used in the control ofsmart robots.The heart of an expert system is a set of facts and rules. In the case of a robotic sys-tem, the facts consist o...

  • Page 686

    named it QNA (which stands for some weird name nobody can ever remember). Sup-pose this molecule, like DNA, could make replicas of itself, so that when you put one ofthem in a glass of water, you’d have a whole glassful in a few days. This molecule wouldbe artificial life, in the sense that it ...

  • Page 687

    3. Second-generation robots first were used around the year:A. 1950.B. 1960.C. 1970.D. 1980.4. The extent to which a machine vision system can differentiate between twoobjects is called the:A. Magnification.B. Sensitivity.C. Selectivity.D. Resolution.5. An automotive robot might best keep itself ...

  • Page 688

    10. Proximity sensing is most closely akin to:A. Direction measurement.B. Epipolar navigation.C. Distance measurement.D. Machine vision.11. A telechir is used in conjunction with:A. An automated guided vehicle.B. Telepresence.C. An insect robot.D. An autonomous robot.12. An absolute limit to the ...

  • Page 689

    17. The region throughout which a robot arm can accomplish tasks is called its:A. Coordinate geometry.B. Reference axis.C. Reference frame.D. Work envelope.18. A robot arm that moves along three independent axes, each of which is straightand perpendicular to the other two, employs:A. Revolute geo...

  • Page 690

    Test: Part fourDo not refer to the text when taking this test.1. A machine vision system that uses two cameras to allow a robot to sense depthis:A. Binaural.B. Binocular.C. Monaural.D. Monocular.E. High resolution.2. A VU meter contains a scale that measures relative:A. Decibels.B. Current.C. Vol...

  • Page 691

    C. An audio mixer.D. A graphic equalizer.E. A phase control.5. The use of a stereo headset to listen to music while driving:A. Is good because it keeps passengers from distracting the driver.B. Is dangerous.C. Keeps the driver’s mind on the road.D. Is good because it prevents road rage.E. Is be...

  • Page 692

    B. A field-effect transistor.C. A junction diode.D. A carbon-composition resistor.E. Digital-to-analog conversion.11. A satellite in a LEO system is usually:A. At an altitude of 22,300 miles.B. Geosynchronous.C. In a retrograde orbit.D. In a polar orbit.E. Midway between the earth and the moon.12...

  • Page 693

    C. 1024 megabits.D. 1024 gigabits.E. None of the above.17. Hexaphonic sound is not common, but if it were, it would most likely be used for:A. True three-dimensional hi-fi audio reproduction.B. Two-way radio communications.C. Ensuring that an AM/FM tuner can receive at least six stations.D. Impro...

  • Page 694

    B. Host.C. Peer.D. Node.E. Destination.23. The term refresh rate refers to:A. The number of times per second that an image is renewed in a computerdisplay.B. The number of times per second that a computer memory contents change.C. The speed at which files on a hard drive are overwritten.D. The nu...

  • Page 695

    28. At low volume levels in an audio amplifier system, the dynamic range is limitedprimarily by the:A. Input impedance.B. Efficiency.C. Input power.D. Noise level.E. Frequency.29. In a wireless system, noise always:A. Improves the bandwidth.B. Increases data transfer rate.C. Reduces the transmitt...

  • Page 696

    E. It can interfere with flight instruments and communications.34. A satellite can remain over the same spot on the earth’s surface at all times:A. Only if it orbits at an altitude of 22,300 miles.B. Only if it is a member of a LEO fleet.C. Only if its orbit is retrograde.D. Only if its orbit i...

  • Page 697

    B. Direction from which the sound is coming.C. Duration of the sound.D. Number of sources from which the sound is coming.E. Waveform of the sound.40. A ratio detector is a circuit for demodulating:A. AM.B. HM.C. FM.D. SSB.E. AFSK.41. A belt drive might be found in a:A. Synthesized AM/FM tuner.B. ...

  • Page 698

    45. Epipolar navigation is a means by which a machine can locate objects and plota course in:A. The total darkness of the deep ocean.B. A straight line.C. Three-dimensional space.D. A circular path.E. The north and south polar regions only.46. The term robot generation refers to:A. The time perio...

  • Page 699

    C. Keep the image from rolling.D. Ensure that the colors are right.E. Keep the image in good focus.A good score is at least 37 correct. Answers are in the back of the book. It’s best tohave a friend check your score the first time, so you won’t memorize the answers ifyou want to take the test...

  • Page 700

    Final examDo not refer to the text when taking this exam.1. As the frequency of ac increases in a coil, the reactance:A. Gets larger negatively.B. Gets smaller negatively.C. Stays the same.D. Gets larger positively.E. Gets smaller positively.2. A beat-frequency oscillator is useful for:A. Generat...

  • Page 701

    5. A utility meter generally measures:A. Watts.B. Amperes.C. Kilowatt hours.D. Kilowatts.E. Volt hours.6. High voltages are better than low voltages for long-distance electric powertransmission because:A. The lines can better withstand lightning strokes.B. The magnetic fields are weaker.C. The el...

  • Page 702

    C. A circle with a line through it.D. A rectangle.E. A D-shaped figure.11. For a given value of capacitance, as the frequency goes down, the reactance:A. Approaches zero from the negative side.B. Gets more and more negative.C. Approaches zero from the positive side.D. Gets more and more positive....

  • Page 703

    B. A personal computer.C. A radio transmitter.D. An electric iron.E. Any of the above.17. In an AM voice signal, the audio information is:A. Exactly at the carrier frequency.B. Contained in sidebands.C. At harmonics of the carrier frequency.D. Rectified before being impressed onto the carrier.E. ...

  • Page 704

    22. Two 400- H inductors are connected in series. There is no mutualinductance. The total inductance is:A. 100 H.B. 200 H.C. 400 H.D. 800 H.E. 1.6 mH.23. The current-carrying part of a field-effect transistor, analogous to a gardenhose in some ways, is called the:A. Source.B. Gate.C. Drain.D. Sou...

  • Page 705

    C. Ohms.D. Gilberts.E. Watts.28. In a pure inductance:A. Current lags voltage by 90 degrees.B. Current lags voltage by less than 90 degrees.C. Current and voltage are in phase.D. Current leads voltage by 90 degrees.E. Current leads voltage by 180 degrees.29. A form of microwave electron tube is:A...

  • Page 706

    B. Avoid the use of sheet metal.C. Use batteries as the source of power.D. Keep wire leads short.E. Use air-core transformers.34. One advantage of ac (compared with dc) as a source of utility power is that:A. It can be used at safer voltage levels.B. It can be easily stepped up or down in voltage...

  • Page 707

    39. A good type of resistor to use in a radio amplifier is:A. Carbon composition.B. Wirewound.C. Silver mica.D. Reactive.E. Tantalum.40. An advantage of machine vision over human vision is the fact that:A. Machines can see at wavelengths to which human eyes are blind.B. Machine vision systems hav...

  • Page 708

    45. A simple power supply filter can be made using:A. A capacitor in parallel with the rectifier output.B. A resistor in parallel with the rectifier output.C. An inductor in parallel with the rectifier output.D. A capacitor in series with the rectifier output.E. A resistor in series with the rect...

  • Page 709

    D. Runs parallel to lines of latitude.E. Is circular in shape.51. One of the main shortcomings of MOSFETs is that they:A. Are easily damaged by static electricity.B. Require high voltages.C. Consume large amounts of current.D. Have very low gain.E. Do not have good sensitivity.52. Resistivity of ...

  • Page 710

    C. SSB.D. FM.E. PCM.57. Antenna efficiency is:A. Usually more important in transmitting systems than in receiving systems.B. The difference between the input and output power.C. A direct function of the noise in a transmitting system.D. The proportion of input power that gets converted into heat....

  • Page 711

    C. 12 ohms.D. 21 ohms.E. Impossible to calculate from this data.63. Three resistors, each of 30 ohms, are connected in parallel. The net resistance is:A. 90 ohms.B. 60 ohms.C. 33 ohms.D. 10 ohms.E. Impossible to determine from the data given.64. The logical statement X YYX depicts:A. The distribu...

  • Page 712

    B. Inversely proportional to the distance between them.C. Not dependent on the distance between them.D. Inversely proportional to their surface area.E. Negligible unless the sheets are both gigantic.69. The forward base bias in a transistor is increased until the collector currentlevels off. This...

  • Page 713

    74. The electron volt is a unit of:A. Voltage.B. Current.C. Power.D. Electric field strength.E. Energy.75. A transformer has a primary-to-secondary turns ratio of 10:1. The input is 120V rms ac. The output is:A. 12 kV rms ac.B. 1.2 kV rms ac.C. 120 V rms ac.D. 12 V rms ac.E. 1.2 V rms ac.76. Wave...

  • Page 714

    C. Multivibrator.D. VCO.E. Clapp circuit.80. The main factor that limits the frequency at which a P-N junction will rectifyis the:A. PIV rating.B. Junction capacitance.C. Junction resistance.D. Junction inductance.E. Reverse bias current.81. The henry is a:A. Very small unit.B. Unit of capacitive...

  • Page 715

    B. Data frequency.C. Data transfer speed.D. Data storage capacity.E. Data communications accuracy.86. In a parallel combination of light bulbs, if one bulb socket totally shorts out:A. The circuit had better have a fuse or a circuit breaker.B. The other bulbs will burn out.C. The other bulbs will...

  • Page 716

    91. In a common-emitter bipolar-transistor circuit:A. The collector is at signal ground.B. The output is taken from the base.C. The emitter is at signal ground.D. The bases of two transistors are connected together.E. The output is taken from the emitter.92. In a certain resistance-capacitance (R...

  • Page 717

    C. 12 dB.D.4 dB.E.6 dB.97. An example of a device that converts electrical energy into visible radiantenergy is:A. A photocell.B. A phototransistor.C. A photovoltaic cell.D. A light-emitting diode.E. A speaker.98. What is the function of bleeder resistors in a power supply?A. To regulate the curr...

  • Page 718

    AAPPENDIXAnswers to quiz, test, andexam questionsChapter 11. B2. C3. D4. D5. D6. A7. B8. C9. A10. B11. C12. A13. D14. C15. C16. A17. C18. B19. C20. DChapter 21. B2. C3. D4. B5. C6. A7. C8. C9. A10. D11. D12. A13. B14. B15. C16. D17. B18. C19. A20. CChapter 31. B2. A3. C4. C5. A6. D7. C8. A9. D10....

  • Page 719

    Chapter 41. A2. C3. D4. A5. B6. D7. C8. A9. C10. A11. D12. B13. D14. B15. A16. C17. C18. A19. D20. BChapter 51. B2. D3. C4. C5. A6. B7. D8. A9. B10. D11. B12. C13. B14. C15. A16. C17. B18. C19. B20. CChapter 61. C2. A3. A4. C5. D6. B7. B8. C9. B10. C11. D12. C13. A14. C15. A16. A17. B18. C19. B20...

  • Page 720

    Test: Part One1. A2. A3. C4. B5. A6. B7. A8. E9. E10. C11. C12. C13. B14. C15. D16. B17. A18. A19. E20. E21. D22. D23. D24. C25. A26. C27. D28. A29. C30. C31. C32. D33. E34. D35. E36. B37. D38. D39. C40. A41. A42. D43. C44. E45. C46. C47. D48. A49. E50. CChapter 91. C2. C3. A4. C5. D6. D7. A8. B9...

  • Page 721

    Chapter 121. C2. A3. B4. B5. D6. B7. D8. C9. A10. B11. B12. D13. C14. A15. C16. B17. D18. C19. D20. CChapter 131. C2. A3. B4. D5. C6. A7. B8. C9. D10. C11. D12. D13. A14. B15. D16. B17. D18. C19. B20. AChapter 141. B2. D3. A4. C5. B6. A7. B8. A9. A10. D11. C12. B13. B14. B15. C16. B17. C18. D19. ...

  • Page 722

    Chapter 171. C2. C3. A4. D5. A6. B7. C8. D9. B10. C11. C12. A13. D14. A15. C16. B17. D18. D19. C20. AChapter 181. C2. A3. D4. B5. B6. A7. C8. D9. A10. D11. B12. B13. C14. D15. C16. A17. C18. D19. B20. BTest: Part Two1. E2. E3. A4. A5. E6. D7. C8. D9. A10. E11. C12. A13. D14. C15. C16. E17. E18. D...

  • Page 723

    Chapter 201. B2. D3. C4. B5. A6. A7. D8. C9. B10. D11. B12. A13. C14. A15. C16. D17. B18. A19. C20. AChapter 211. C2. D3. B4. A5. B6. C7. A8. B9. D10. C11. A12. D13. D14. B15. C16. A17. C18. B19. A20. CChapter 221. D2. A3. B4. D5. D6. C7. B8. C9. B10. D11. C12. A13. C14. D15. A16. D17. B18. C19. ...

  • Page 724

    Chapter 251. C2. B3. A4. C5. A6. C7. D8. C9. D10. B11. A12. B13. D14. C15. D16. D17. B18. A19. D20. CChapter 261. C2. A3. C4. C5. A6. B7. D8. B9. C10. D11. B12. C13. A14. B15. D16. D17. A18. B19. A20. DChapter 271. C2. C3. A4. C5. D6. C7. B8. A9. C10. D11. C12. A13. D14. B15. B16. B17. D18. A19. ...

  • Page 725

    Chapter 301. C2. A3. D4. D5. C6. A7. B8. B9. B10. D11. C12. A13. D14. A15. C16. C17. D18. A19. D20. BTest: Part Three1. E2. B3. A4. C5. A6. C7. A8. D9. E10. D11. D12. B13. C14. C15. D16. C17. B18. E19. B20. D21. C22. E23. A24. B25. D26. A27. C28. E29. A30. D31. C32. C33. C34. B35. E36. D37. A38. ...

  • Page 726

    Chapter 331. B2. A3. D4. C5. A6. C7. D8. A9. D10. C11. A12. D13. B14. C15. A16. C17. B18. A19. D20. AChapter 341. B2. A3. D4. D5. C6. B7. D8. B9. D10. C11. B12. A13. D14. C15. C16. B17. D18. C19. B20. BTest: Part Four1. B2. A3. A4. C5. B6. C7. B8. E9. D10. A11. D12. C13. B14. C15. B16. E17. A18. ...

  • Page 727

    21. D22. D23. E24. C25. B26. E27. E28. A29. C30. C31. E32. A33. D34. B35. B36. A37. E38. A39. A40. A41. C42. E43. C44. C45. A46. D47. D48. E49. E50. B51. A52. C53. B54. B55. B56. D57. A58. D59. C60. E61. E62. A63. D64. C65. A66. B67. D68. B69. B70. D71. E72. E73. B74. E75. D76. A77. C78. C79. C80...

  • Page 728

    BAPPENDIXSchematic symbols707AmmeterAmplifier generalAmplifier, invertingAmplifier, operationalAND gateAntenna, balancedAntenna, generalAntenna, loopAntenna, loop, multiturnBatteryCapacitor, feedthroughCapacitor, fixedCapacitor, variableCapacitor, variable, split-rotorCapacitor, variable, split-s...

  • Page 729

    DiacDiode, field-effectDiode, generalDiode, GunnDiode, light-emittingDiode, photosensitiveDiode, PINDiode, SchottkyDiode, tunnelDiode, varactorDiode, zenerDirectional couplerDirectional wattmeterExclusive-OR gateFemale contact, generalFerrite beadFilament, electron-tubeFuseGalvanometerGrid, elect...

  • Page 730

    Inductor, powdered-iron core, tappedInductor, powdered-iron core, variableIntegrated circuit, generalJack, coaxial or phonoJack, phone, two-conductorJack, phone, three-conductorKey, telegraphLamp, incandescentLamp, neonMale contact, generalMeter, generalMicroammeterMicrophoneMicrophone, direction...

  • Page 731

    Positive voltage connectionPotentiometerProbe, radio-frequencyRectifier, gas-filledRectifier, high-vacuumRectifier, semiconductorRectifier, silicon-controlledRelay, double-pole, double-throwRelay, double-pole, single-throwRelay, single-pole, double-throwRelay, single-pole, single-throwResistor, f...

  • Page 732

    Switch, single-pole, rotarySwitch, single-pole, double-throwSwitch, single-pole, single-throwTerminals, general, balancedTerminals, general, unbalancedTest pointThermocoupleTransformer, air coreTransformer, air core, step-downTransformer, air core, step-upTransformer, air core, tapped primaryTran...

  • Page 733

    TriacTube, diodeTube, heptodeTube, hexodeTube, pentodeTube, photosensitiveTube, tetrodeTube, triodeVoltmeterWattmeterWaveguide, circularWaveguide, flexibleWaveguide, rectangularWaveguide, twistedWires, crossing, connectedWires, crossing, not connected712 Appendix B

  • Page 734

    Suggested additionalreferenceCrowhurst, N., and Gibilisco, S., Mastering Technical Mathematics, 2d ed. NewYork: McGraw-Hill, 1999.Dorf, R., Electrical Engineering Handbook, 2d ed. Boca Raton, Fla.: CRC Press,1997.Gibilisco, S., Electronics Portable Handbook. New York: McGraw-Hill, 1999.Gibilisco,...

  • Page 735

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  • Page 736

    715IndexAabsolute value:complex numbers and, 267–268impedance, 272acceptor impurity, 362acoustic emitter, 612acoustic pickup, 612acoustic transducers, 612–613acoustics, 583–585admittance, 276–280complex in parallel, 289–292converting to impedance, 294GB plane, 277–279parallel circuits...

  • Page 737

    716 Indexaudio amplifiers, 446–447frequency response, 446–447volume control, 447audio frequency (AF), 467inductors at, 193audio-frequency-shift keying(AFSK), 477, 532audio-frequency transformers, 336audio mixer, 593–595audio oscillators, 468–469audio potentiometer, 106–107audio tape, 14...

  • Page 738

    Index717circuits:analysis of dc, 82–98dc, 65–81GLC, 292–294integrated (see integrated circuits)power distribution in parallel,88–89power distribution in series, 88RC, 255–256RL, 238RLC, 284–304transistors abbreviations for, 428voltage/current/resistance, 68Clapp oscillator, 461–463c...

  • Page 739

    718 Indexdemodulation (Cont.)frequency-shift keying, 506pulse modulation, 508–509single sideband, 506depletion mode, 418vs. enhancement mode, 425destination computer, 637, 638detection (see demodulation)detection diodes, 371–372diamagnetism, 142dielectric, 13, 193, 204, 493diffusion, 417digit...

  • Page 740

    Index719fast-scan television (FSTV),489–490feedback, 458ferrite cores, 190, 330ferromagnetism, 39, 142, 135–136FET amplifier, 438–439FET voltmeter (FETVM), 54fiberoptics, 378, 494–495field coil, 146field-effect transistor (FET), 54,416–432insulated-gate, 423junction, 416–422metal-oxid...

  • Page 741

    720 Indexinductance, 183–198amount of lag, 240–243line, 193–195mutual, 188–189permeability tuning, 190property of, 183–184pure, 237resistance and, 238–239stray, 195unit of, 185unwanted, 195induction, electromagnetic, 327inductive reactance, 231–246current lags voltage, 237frequency ...

  • Page 742

    Index721magnetic field, 136magnetic field strength, 139–141ampere-turn/gilbert units, 140electromagnets, 140–141tesla/gauss units, 139magnetic force, 135–136magnetic levitation, 136magnetic polarity, 38, 137–138magnetic tape, analog, 599–601magnetic units, 39–40magnetism, 19, 38–39,...

  • Page 743

    722 Indexoscillators (Cont.)concept, 458crystal-controlled, 464–465diode, 467feedback, 458Hartley, 459–461IC, 469parasitic, 545performance reliability, 464Pierce, 464PLL frequency synthesizer, 466stability, 463–464uses, 457variable-frequency, 463–464voltage-controlled, 376, 465–466oscil...

  • Page 744

    Index723RR-S flip-flops, 565rack hi-fi system, 589radians of phase, 172, 221radiation:coherent, 378cosmic, 18electromagnetic, 166radiation resistance, 323radio frequency (RF):classifications, 494inductors at, 193power amplifiers, 544–545radio-frequency amplifiers,450–452weak-signal vs. power,...

  • Page 745

    724 Indexsaturation, 190, 378, 403color, 597, 632–633sawtooth wave, 167–169fast-rise/slow-decay, 167slow-rise/fast-decay, 168variable-rise/variable-decay, 169schematic diagrams, 67vs. wiring diagrams, 68schematic symbols, 65–67scientific notation, 34second-generation robot, 645sectors, 592,...

  • Page 746

    Index725transformers (Cont.)radio-frequency, 339–341reactance, 341–342step-up/step-down, 327turns ratio, 328–329utility, 330–331Variac, 393transient suppressors, 394transistors:bipolar, 400–415circuit abbreviations, 428field-effect, 54, 416–432NPN vs. PNP, 400–401transistor-transist...

  • Page 747

    726 Indexwire:resistivity, 26–27(See also transmission lines)wireless local area networks,615–616wireless security systems, 616–617wirewound resistors, 103–104wiring diagrams, 68World Wide Web, 640XXNOR gate, 560, 561XOR gate, 560, 562ZZener diodes, 366, 374, 392zero bias, 402–403Zip di...

  • Page 748

    About the AuthorStan Gibilisco is a popular and respected electronics and science author specializingin reference works. His Encyclopedia of Electronics was named a “Best Referenceof the 1980s” by the American Library Association. A former radio engineer andtechnical writer in electronics, he...