TRANSISTOR AUDIO POWER AMPLIFIERS Questions :-
1. The output stage of a multistage amplifier is also called ……………
Mixer stage
Power stage
Detector stage
F stage
Ans : 2
2. ………………. coupling is generally employed in power amplifiers
Transformer
RC
direct
Impedance
Ans : 1
3. A class A power amplifier uses …………
Two transistors
Three transistors
One transistor
None of the above
Ans : 3
4. The maximum efficiency of resistance loaded class A power amplifier is ……..
5%
50%
30%
25%
Ans : 4
5. The maximum efficiency of transformer coupled class A power amplifier is ………………
30%
50%
80%
45%
Ans : 2
6. Class……. power amplifier has the highest collector efficiency
C
A
B
AB
Ans : 1
7. Power amplifiers handle …………. signals compare to voltage amplifiers
Small
Very small
Large
None of the above
Ans : 3
8. 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
Ans : 2
9. Class C amplifiers are used as …………….
AF amplifiers
Detectors
F. amplifiers
None of the above
Ans : 3
10. A power amplifier has comparatively …………….. ß
Small
Large
Very large
None of the above
Ans : 1
11. The maximum collector efficiency of class B operation is ……………..
50%
90%
5%
5%
Ans : 4
12. A 2-transistor class B power amplifier is commonly called ……….. amplifier
Dual
Push-pull
Symmetrical
Differential
Ans : 2
13. If a transistor is operated in such a way that output current flows for 60o of the input signal, then it is …………… operation
Class A
Class B
Class C
None of the above
Ans : 3
14. 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
Ans : 4
15. When a transistor is cut off……………..
Maximum voltage appears across transistor
Maximum current flows
Maximum voltage appears across load
None of the above
Ans : 1
16. A class A power amplifier is sometimes called ………….. amplifier
Symmetrical
Single-ended
Reciprocating
Differential
Ans : 2
17. Class ………….. operation gives the maximum distortion
A
B
C
AB
Ans : 3
18. The output stage of a multistage amplifier usually employs ………..
Push-pull amplifier
Preamplifier
Class A power amplifier
None of the above
Ans : 1
19. The size of a power transistor is made considerably large to …………
Provide easy handling
Dissipate heat
Facilitate connections
None of the above
Ans : 2
20. Low efficiency of a power amplifier results in ……………….
Low forward bias
Less battery consumption
More battery consumption
None of the above
Ans : 3
21. The driver stage usually employs………….
Class A power amplifier
Push-pull amplifier
Class C amplifier
None of the above
Ans : 1
22. If the power rating of a transistor is 1W and collector current is 100mA, then maximum allowable collector voltage is ………..
1V
100V
20V
10V
Ans : 4
23. When no signal is applied, the approximate collector efficiency of class A power amplifier is …….
10%
0%
25%
50%
Ans : 2
24. 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%
Ans : 3
25. 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
Ans : 1
26. 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
Ans : 4
27. 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
Ans : 2
28. The push-pull circuit must use …………… operation
Class A
Class C
Class B
Class AB
Ans : 3
29. 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
Ans : 1
30. What turn ratio (Np/Ns) of transformer is required to match 4 O speaker to a transistor having an output impedance of 8000 O?
2
7
3
None of the above
Ans : 2
31. A transformer coupled class A power amplifier has a load of 100 O on the secondary. If the turn ratio is 10:1, what is the value of load appearing on the primary?
5 kO
20 kO
100 kO
10 kO
Ans : 4
32. Power amplifiers generally use transformer coupling because transformer permits……..
Cooling of the circuit
Impedance matching
Distortionless output
Good frequency response
Ans : 2
33. Transformer coupling can be used in …………… amplifiers
Either power or voltage
Only power
Only voltage
None of the above
Ans : 1
34. The output transformer used in a power amplifier is a ……………. transformer
1:1 ratio
Step-up
Step-down
None of the above
Ans : 3
35. The most important consideration in power amplifier is ………..
Biasing the circuit
Collector efficiency
To keep the transformer cool
None of the above
Ans : 2
36. An AF amplifier is shielded to …………
Keep the amplifier cool
Protect from rusting
Prevent induction due to stray magnetic fields
None of the above
Ans : 3
37. The pulsating d.c. applied to power amplifier causes ……………..
Burning of transistor
Hum in the circuit
Excessive forward voltage
None of the above
Ans : 2
38. The disadvantage of impedance matching is that it ………………….
Gives distorted output
Gives low power output
Requires a transformer
None of the above
Ans : 1
39. If the gain versus frequency curve of a transistor amplifier is not flat, then there is distortion.
Amplitude
Intermodulation
Frequency
None of the above
Ans : 3
40. The most costly coupling is ……………… coupling
RC
Direct
Impedance
Transformer
Ans : 4