Question

Experiment 7 BJT Power Amplifiers ipolar junction transistors when used as power amplifiers must be able to provide power to drive a load -anywhere from a few watts to hundreds of watts. Heat dissipation and efficiency are considerations with any power amplifier including BJT power amplifiers. Except in low-power applications, the class-A amplifier is not widely used because it is not particularly efficient. In Part 1 of this experiment, you will measure the power gain and efficiency of a simple class-A power amplifier. The amplifier you will test uses a Darlington arrangement of transistors to improve the power gain. The total power is low to avoid heat, which is associated with power amplifiers. In Part 2, you will construct a class-B (push-pull) amplifier. The class-B amplifier is much more efficient than the class A amplifier in part 1. Crossover distortion is observed, and then it is eliminated with a circuit called a diode current- mirror to bias the transistors into slight conduction. The forward-biased diodes wilI each have approximately the same 0.7 V drop as the base-emitter junction. The circuit is modified to one that is similar to the Device Application in the text but uses lower power to avoid heating problems and is simplified to make your lab time efficient. Reading Floyd, Electronic Devices, Tenth Edition, Chapter 7 Key Objectives Part 1: Calculate and measure the dc and ac characteristics for a class-A amplifier. Part 2: Calculate and measure the de and ac characteristics for a class-B amplifier.

Answer 1

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