Power amplifiers

Question 1

How is efficiency of an amp calculated?

Answer 1

(Ac power out / DCpower in) x100

Question 2

What does 100% efficiency of an op amp mean

Answer 2

All DC power is converted to AC power, otherwise it is dissipated as heat

Question 3

Explain why biasing is important for amplifiers

Answer 3

-to achieve AC cycle, the voltage should be set Vcc/2 so Vout can fluctuate upwards and downwards

-the transistor is biased by choosing the resistor values at the collector and base

Question 4

Explain why class A amps have the worst efficiency

Answer 4

-Transistors in class A amps conduct during the entire input cycle
-due to constant conduction, this leads to heat generation

Question 5

Explain how class B amps operate

Answer 5

-The q point is selected so there is no collector current when there is no signal
-the q point is set at the collector cut-off voltage
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