Multiple Choice Questions and Answers on Transistor Audio Power Amplifiers

Multiple Choice Questions and Answers on Transistor Audio Power Amplifiers

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

  1. Mixer stage
  2. Power stage
  3. Detector stage
  4. F stage

Answer : 2

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

  1. Transformer
  2. RC
  3. direct
  4. Impedance

Answer : 1

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

  1. Two transistors
  2. Three transistors
  3. One transistor
  4. None of the above

Answer : 3

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

  1. 5%
  2. 50%
  3. 30%
  4. 25%

Answer : 4

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

  1. 30%
  2. 50%
  3. 80%
  4. 45%

Answer : 2

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

  1. C
  2. A
  3. B
  4. AB

Answer : 1

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

  1. Small
  2. Very small
  3. Large
  4. None of the above

Answer : 3

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

  1. At cut off point
  2. At the middle
  3. At saturation point
  4. None of the above

Answer : 2

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

  1. AF amplifiers
  2. Detectors
  3. F. amplifiers
  4. None of the above

Answer : 3

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

  1. Small
  2. Large
  3. Very large
  4. None of the above

Answer : 1

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

  1. 50%
  2. 90%
  3. 5%
  4. 5%

Answer : 4

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

  1. Dual
  2. Push-pull
  3. Symmetrical
  4. Differential

Answer : 2

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

  1. Class A
  2. Class B
  3. Class C
  4. 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 ……………….

  1. 5 W
  2. 33 W
  3. 75 W
  4. 1 W

Answer : 4

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

  1. Maximum voltage appears across transistor
  2. Maximum current flows
  3. Maximum voltage appears across load
  4. None of the above

Answer : 1

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

  1. Symmetrical
  2. Single-ended
  3. Reciprocating
  4. Differential

Answer : 2

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

  1. A
  2. B
  3. C
  4. AB

Answer : 3

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

  1. Push-pull amplifier
  2. Preamplifier
  3. Class A power amplifier
  4. None of the above

Answer : 1

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

  1. Provide easy handling
  2. Dissipate heat
  3. Facilitate connections
  4. None of the above

Answer : 2

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

  1. Low forward bias
  2. Less battery consumption
  3. More battery consumption
  4. None of the above

Answer : 3

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

  1. Class A power amplifier
  2. Push-pull amplifier
  3. Class C amplifier
  4. 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 ………..

  1. 1V
  2. 100V
  3. 20V
  4. 10V

Answer : 4

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

  1. 10%
  2. 0%
  3. 25%
  4. 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?

  1. 20%
  2. 80%
  3. 40%
  4. 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. 1 W
  2. 2 W
  3. 4 W
  4. 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 ?

  1. 10 W
  2. 15 W
  3. 5 W
  4. 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?

  1. 10 W
  2. 4 W
  3. 8 W
  4. None of the above

Answer : 2

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

  1. Class A
  2. Class C
  3. Class B
  4. 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?

  1. 20 W
  2. 40 W
  3. 10 W
  4. 80 W

Answer : 1

Q30. What turn ratio (Np/Ns) of transformer is required to match 4 Ω speaker to a transistor having an output impedance of 8000 Ω?

  1. 2
  2. 7
  3. 3
  4. 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?

  1. 5 kΩ
  2. 20 kΩ
  3. 100 kΩ
  4. 10 kΩ

Answer : 4

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

  1. Cooling of the circuit
  2. Impedance matching
  3. Distortionless output
  4. Good frequency response

Answer : 2

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

  1. Either power or voltage
  2. Only power
  3. Only voltage
  4. None of the above

Answer : 1

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

  1. 1:1 ratio
  2. Step-up
  3. Step-down
  4. None of the above

Answer : 3

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

  1. Biasing the circuit
  2. Collector efficiency
  3. To keep the transformer cool
  4. None of the above

Answer : 2

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

  1. Keep the amplifier cool
  2. Protect from rusting
  3. Prevent induction due to stray magnetic fields
  4. None of the above

Answer : 3

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

  1. Burning of transistor
  2. Hum in the circuit
  3. Excessive forward voltage
  4. None of the above

Answer : 2

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

  1. Gives distorted output
  2. Gives low power output
  3. Requires a transformer
  4. None of the above

Answer : 1

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

  1. Amplitude
  2. Intermodulation
  3. Frequency
  4. None of the above

Answer : 3

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

  1. RC
  2. Direct
  3. Impedance
  4. Transformer

Answer : 4

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