GROL Amplifier and Oscillator Circuits 3

Question 1

What is the theoretical maximum efficiency of a Class A power amplifier?

Accepted Answer

50%

Answer

A Class A amplifier biased at the center of its load line has a theoretical maximum efficiency of 50%, though practical circuits typically achieve far less.

Question 2

Crossover distortion in a Class B push-pull amplifier is caused by:

Accepted Answer

A dead zone near zero crossing where neither transistor conducts

Answer

Crossover distortion occurs because each transistor has a turn-on threshold voltage, creating a brief gap in conduction near the zero crossing of the waveform.

Question 3

Why are Class C amplifiers used for RF power amplification but not audio amplification?

Accepted Answer

Their high efficiency works with a resonant tank circuit that reconstructs the full sine wave

Answer

Class C amplifiers are very efficient because they conduct for less than 180° of the cycle; the resonant tank circuit stores energy and restores the complete sine wave output.

Question 4

The conduction angle of a properly biased Class A amplifier is:

Accepted Answer

360°

Answer

Class A amplifiers are biased so the transistor conducts for the full 360° of the input cycle — the transistor never cuts off.

Question 5

Class AB amplifiers are preferred over Class B in high-fidelity audio applications because they:

Accepted Answer

Reduce crossover distortion while maintaining better efficiency than Class A

Answer

Class AB biases the transistors slightly into conduction, eliminating the crossover distortion of Class B while still being more efficient than Class A.

(GROL) General Radiotelephone Operator License Practice Test

(GROL) General Radiotelephone Operator License Practice Test

GROL Amplifier and Oscillator Circuits 3