Electronic Devices-Power Amplifiers
Electronic Devices-Power Amplifiers
31. Which of the following describe(s) a power amplifier?
- It can handle large power.
- It can handle large current.
- It does not provide much voltage gain.
- All of the above
32. Categorize the power efficiency of each class of amplifier, from worst to best.
- A, B, AB, D
- A, AB, D, B
- A, AB, B, D
33. In a class AB amplifier, if the VBE drops are not matched to the diode drops or if the diodes are not in thermal equilibrium with the transistors, this can result in
- a current mirror.
- diode separation.
- crossover distortion.
- thermal runaway.
34. The least efficient amplifier among all classes is
- class B.
- class A.
- class AB.
- class C.
35. In practice, the efficiency of a capacitively coupled class A amplifier is about ________%.
- 25
- 40
- 70
- 10
36. A class A amplifier has a voltage gain of 30 and a current gain of 25. What is the power gain?
- 30
- 25
- 1.2
- 750
37. Which of the following transistors has been quite popular as the driver device for class D amplification?
- BJT
- FET
- UJT
- MOSFET
38. Which of the following is (are) the disadvantage(s) of a class B complementary-symmetry circuit?
- It needs two separate voltage sources.
- There is crossover distortion in the output signal.
- It does not provide exact switching of one transistor off and the other on at the zero-voltage condition.
- All of the above
39. Which of the power amplifiers has the lowest overall efficiency?
- Class A
- Class B or AB
- Class C
- Class D
40. Calculate the efficiency of a class B amplifier for a supply voltage of VCC = 20 V with peak output voltage of VL(p) = 18 V. Assume RL = 16.
- 78.54%
- 75%
- 70.69%
- 50%