## Multiple Choice Questions and Answers on Transistor Audio Power Amplifiers

**Q1. The output stage of a multistage amplifier is also called ……………**

- Mixer stage
- Power stage
- Detector stage
- F stage

**Answer : 2**

**Q2. ………………. coupling is generally employed in power amplifiers**

- Transformer
- RC
- direct
- Impedance

**Answer : 1**

**Q3. A class A power amplifier uses …………**

- Two transistors
- Three transistors
- One transistor
- None of the above

**Answer : 3**

**Q4. The maximum efficiency of resistance loaded class A power amplifier is ……..**

- 5%
- 50%
- 30%
- 25%

**Answer : 4**

**Q5. The maximum efficiency of transformer coupled class A power amplifier is ………………**

- 30%
- 50%
- 80%
- 45%

**Answer : 2**

**Q6. Class……. power amplifier has the highest collector efficiency**

- C
- A
- B
- AB

**Answer : 1**

**Q7. Power amplifiers handle …………. signals compare to voltage amplifiers**

- Small
- Very small
- Large
- None of the above

**Answer : 3**

**Q8. In class A operation, the operating point is generally located ………. of the d.c. load line. **

- At cut off point
- At the middle
- At saturation point
- None of the above

**Answer : 2**

**Q9. Class C amplifiers are used as …………….**

- AF amplifiers
- Detectors
- F. amplifiers
- None of the above

**Answer : 3**

**Q10. A power amplifier has comparatively …………….. β**

- Small
- Large
- Very large
- None of the above

**Answer : 1**

**Q11. The maximum collector efficiency of class B operation is ……………..**

- 50%
- 90%
- 5%
- 5%

**Answer : 4**

**Q12. A 2-transistor class B power amplifier is commonly called ……….. amplifier**

- Dual
- Push-pull
- Symmetrical
- Differential

**Answer : 2**

**Q13. If a transistor is operated in such a way that output current flows for 60 ^{o }of the input signal, then it is …………… operation**

- Class A
- Class B
- Class C
- None of the above

**Answer : 3**

**Q14. If the zero signal dissipation of a transistor is 1W, then power rating of the transistor should be at least ……………….**

- 5 W
- 33 W
- 75 W
- 1 W

**Answer : 4**

**Q15. When a transistor is cut off……………..**

- Maximum voltage appears across transistor
- Maximum current flows
- Maximum voltage appears across load
- None of the above

**Answer : 1**

**Q16. A class A power amplifier is sometimes called ………….. amplifier**

- Symmetrical
- Single-ended
- Reciprocating
- Differential

**Answer : 2**

**Q17. Class ………….. operation gives the maximum distortion**

- A
- B
- C
- AB

**Answer : 3**

**Q18. The output stage of a multistage amplifier usually employs ………..**

- Push-pull amplifier
- Preamplifier
- Class A power amplifier
- None of the above

**Answer : 1**

**Q19. The size of a power transistor is made considerably large to …………**

- Provide easy handling
- Dissipate heat
- Facilitate connections
- None of the above

**Answer : 2**

**Q20. Low efficiency of a power amplifier results in ……………….**

- Low forward bias
- Less battery consumption
- More battery consumption
- None of the above

**Answer : 3**

**Q21. The driver stage usually employs………….**

- Class A power amplifier
- Push-pull amplifier
- Class C amplifier
- None of the above

**Answer : 1**

**Q22. If the power rating of a transistor is 1W and collector current is 100mA, then maximum allowable collector voltage is ………..**

- 1V
- 100V
- 20V
- 10V

**Answer : 4**

**Q23. When no signal is applied, the approximate collector efficiency of class A power amplifier is …….**

- 10%
- 0%
- 25%
- 50%

**Answer : 2**

**Q24. What will be the collector efficiency of a power amplifier having zero signal power dissipation of 5 watts and a.c. power output of 2 watts?**

- 20%
- 80%
- 40%
- 50%

**Answer : 3**

**Q25. The output signal voltage and current of a power amplifier are 5V and 200 mA; the values being r.m.s. What is the power output?**

- 1 W
- 2 W
- 4 W
- None of the above

**Answer : 1**

**Q26. The maximum a.c. power output from a class A power amplifier is 10 W. What should be the minimum power rating of the transistor used ?**

- 10 W
- 15 W
- 5 W
- 20 W

**Answer : 4**

**Q27. For the same a.c. power output as above, what should be the minimum power rating of transistor for class B operation?**

- 10 W
- 4 W
- 8 W
- None of the above

**Answer : 2**

**Q28. The push-pull circuit must use …………… operation**

- Class A
- Class C
- Class B
- Class AB

**Answer : 3**

**Q29. The class B push-pull circuit can deliver 100 W of a.c. output power. What should be the minimum power rating of each transistor?**

- 20 W
- 40 W
- 10 W
- 80 W

**Answer : 1**

**Q30. What turn ratio (N _{p}/N_{s}) of transformer is required to match 4 Ω speaker to a transistor having an output impedance of 8000 Ω?**

- 2
- 7
- 3
- None of the above

**Answer : 2**

**Q31. A transformer coupled class A power amplifier has a load of 100 Ω on the secondary. If the turn ratio is 10:1, what is the value of load appearing on the primary?**

- 5 kΩ
- 20 kΩ
- 100 kΩ
- 10 kΩ

**Answer : 4**

**Q32. Power amplifiers generally use transformer coupling because transformer permits……..**

- Cooling of the circuit
- Impedance matching
- Distortionless output
- Good frequency response

**Answer : 2**

**Q33. Transformer coupling can be used in …………… amplifiers**

- Either power or voltage
- Only power
- Only voltage
- None of the above

**Answer : 1**

**Q34. The output transformer used in a power amplifier is a ……………. transformer**

- 1:1 ratio
- Step-up
- Step-down
- None of the above

**Answer : 3**

**Q35. The most important consideration in power amplifier is ………..**

- Biasing the circuit
- Collector efficiency
- To keep the transformer cool
- None of the above

**Answer : 2**

**Q36. An AF amplifier is shielded to …………**

- Keep the amplifier cool
- Protect from rusting
- Prevent induction due to stray magnetic fields
- None of the above

**Answer : 3**

**Q37. The pulsating d.c. applied to power amplifier causes ……………..**

- Burning of transistor
- Hum in the circuit
- Excessive forward voltage
- None of the above

**Answer : 2**

**Q38. The disadvantage of impedance matching is that it ………………….**

- Gives distorted output
- Gives low power output
- Requires a transformer
- None of the above

**Answer : 1**

**Q39. If the gain versus frequency curve of a transistor amplifier is not flat, then there is distortion.**

- Amplitude
- Intermodulation
- Frequency
- None of the above

**Answer : 3**

**Q40. The most costly coupling is ……………… coupling**

- RC
- Direct
- Impedance
- Transformer

**Answer : 4**