Understanding Diodes

Chapter Understanding Diodes

Complete Electronics Self Teaching Guide with Projects
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Complete Electronics Self Teaching Guide with Projects

  • CHAPTER 2 THE DIODE48of adjacent regions of semiconductor crystals, which allow the manufacture of small diodes, as well as transistors and integrated circuits.When you complete this chapter, you can do the following: ■ Specify the uses of diodes in DC circuits. ■ Determine from a circuit diagram whether a diode is forward- or reverse-biased. ■ Recognize the characteristic V-I curve for a diode. ■ Specify the knee voltage for a silicon or a germanium diode. ■ Calculate current and power dissipation in a diode. ■ Define diode breakdown. ■ Differentiate between zeners and other diodes. ■ Determine when a diode can be considered “perfect.”UNDERSTANDING DIODES1  Silicon and germanium are semiconductor materials used in the manufacture of diodes, transistors, and integrated circuits. Semiconductor material is refined to an extreme level of purity, and then minute, controlled amounts of a specific impurity are added (a process called doping). Based on which impurity is added to a region of a semiconductor crystal, that region is said to be N type or P type. In addition to electrons (which are negative charge carriers used to conduct charge in a conventional conductor), semiconductors contain positive charge carriers called holes. The impurities added to an N type region increases the number of electrons capable of conducting charge, whereas the impurities added to a P type region increase the number of holes capable of conducting charge.When a semiconductor chip contains an N doped region adjacent to a P doped region, a diode junction (often called a PN junction) is formed. Diode junctions can also be made with either silicon or germanium. However, silicon and germanium are never mixed when making PN junctions.QUESTIONWhich diagrams in Figure 2.1 show diode junctions? Book Authorc02V107/04/2012 2:49 PM c02.indd 487/4/2012 2:49:37 PM