What is Amplifier gain

Chapter 1.4 Amplifier gain

Lessons In Electric Circuits Volume III – Semiconductors Book
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Lessons In Electric Circuits Volume III – Semiconductors Book

  • 6CHAPTER 1. AMPLIFIERS AND ACTIVE DEVICESPinputPoutputAmplifierExternalpower sourceFigure 1.5:While an amplifier can scale a small input signal to large output, its energy sourceis an external power supply.or less, one can never be made to function as a “perpetual motion” device.The requirement of an external source of power is common to all types of amplifiers, elec-trical and non-electrical. A common example of a non-electrical amplification system wouldbe power steering in an automobile, amplifying the power of the driver’s arms in turning thesteering wheel to move the front wheels of the car. The source of power necessary for the am-plification comes from the engine. The active device controlling the driver’s “input signal” is ahydraulic valve shuttling fluid power from a pump attached to the engine to a hydraulic pistonassisting wheel motion. If the engine stops running, the amplification system fails to amplifythe driver’s arm power and the car becomes very difficult to turn.1.4Amplifier gainBecause amplifiers have the ability to increase the magnitude of an input signal, it is useful tobe able to rate an amplifier’s amplifying ability in terms of an output/input ratio. The technicalterm for an amplifier’s output/input magnitude ratio is gain. As a ratio of equal units (powerout / power in, voltage out / voltage in, or current out / current in), gain is naturally a unitlessmeasurement. Mathematically, gain is symbolized by the capital letter “A”.For example, if an amplifier takes in an AC voltage signal measuring 2 volts RMS andoutputs an AC voltage of 30 volts RMS, it has an AC voltage gain of 30 divided by 2, or 15:AV = VoutputVinputAV = 30 V2 VAV = 15Correspondingly, if we know the gain of an amplifier and the magnitude of the input signal,we can calculate the magnitude of the output. For example, if an amplifier with an AC current