In this section of Electronic Devices and Circuits.It contain Transistor Power Amplifiers MCQs (Multiple Choice Questions Answers).All the MCQs (Multiple Choice Question Answers) requires in depth reading of Electronic Devices and Circuits Subject as the hardness level of MCQs have been kept to advance level.These Sets of Questions are very helpful in Preparing for various Competitive Exams and University level Exams.
This Section covers below lists of topics :
- Transistor Power Amplifiers MCQs.
- Voltage and Power Amplifier MCQs.
- Push-pull amplifier MCQs.
- Harmonic Distortion in Power amplifier MCQs.
- Distortion in Push-Pull amplifiers MCQs.
Practice it now to sharpen your concept.
PRACTICE IT NOW TO SHARPEN YOUR CONCEPT AND KNOWLEDGE
1. Heat sinks are used with power transistors to
- To increases the collector dissipation rating of the transistor
- Increase the gain of the transistor
- Increase the output power
- Reduces the heat loses in the transistor
A. To increases the collector dissipation rating of the transistor
2. The maximum efficiency of class –B amplifier is
- 50%
- 78.5%
- 35%
- 100%
B. 78.5%
3. The collector current in quiescent condition is zero when
- The amplifier is working in class A operation
- The amplifier is working class B operation
- The amplifier is working on class AB operation
- None of these
B. The amplifier is working class B operation
4. The output power of a power amplifiers is several times its input power .it is so because
- Step up transformer is used at the out put
- Transistor act as a source of power
- Power amplifier introduces positive feedback
- Power amplifier converts a part of input dc power into ac output power
D. Power amplifier converts a part of input dc power into ac output power
5. A push pull amplifier
- Reduces odd harmonies in the output
- Is the first stage of audio amplifier?
- Reduces even harmonies in the output
- Uses single transistor
C. Reduces even harmonies in the output
6. The main function of a transformer employed at the output of power amplifiers is
- To increase the voltage gain
- To step up the voltage and power
- To match the load impedance with the dynamic output impedance of the transistor for maximum power transfer
- To safeguard the transistor against overheating
C. To match the load impedance with the dynamic output impedance of the transistor for maximum power transfer
7. Usually, a push pull amplifier is used at the output stage of an audio amplifier, the stage that just precedes the output stage is
- Voltage amplification stage
- Current amplification stage
- Driver stage
- None of these
C. Driver stage
8. In push pull amplifiers, usually biasing is not required because
- Dc battery Vcc is employed
- Power transistors do not require biasing
- Heat sink is used with the transistor
- Transistors are working in class-B operation
D. Transistors are working in class-B operation
9. The criteria for the selection of output transformer is
- That transformer should be step up transformer to get more voltage gain
- That transformer should be step down transformer to get more power gain
- That the turn ratio of the transformer should be such that proper impedance can be obtained
- None of these
C. That the turn ratio of the transformer should be such that proper impedance can be obtained
10. The resistance of a loudspeaker is usually
- A few ohms
- A few hundred ohms
- A few kilo ohms
- A few mega ohms
A. A few ohms
11. An emitter follower has a voltage gain that is
- Much less than one
- Approximately equal to one
- Greater than one
- Zero
B. Approximately equal to one
12. The total ac emitter resistance of an emitter follower equals
- re’
- re
- re + re’
- RE
C. re + re’
13. The input impedance of the base of an emitter follower is usually
- Low
- High
- Shorted to ground
- Open
B. High
14. The dc emitter current for class A emitter followers is
- The same as the ac emitter current
- VE divided by RE
- Vc divided by Rc
- The same as the load current
B. VE divided by RE
15. The ac base voltage of an emitter follower is across the
- Emitter diode
- DC emitter resistor
- Load resistor
- Emitter diode and external ac emitter resistance
D. Emitter diode and external ac emitter resistance
16. The output voltage of an emitter follower is across the
- Emitter diode
- DC collector resistor
- Load resistor
- Emitter diode and external ac emitter resistance
C. Load resistor
17. If Beta = 200 and re = 150 ohm, the input impedance of the base is approximately
- 30 kohm
- 600 n
- 3 kohm
- 5 kohm
A. 30 kohm
18. The input voltage to an emitter follower is usually
- Less than the generator voltage
- Equal to the generator voltage
- Greater than the generator voltage
- Equal to the supply voltage
A. Less than the generator voltage
19. The ac emitter current is closest to
- VG divided by re
- Vin divided by re’
- VG divided by re’
- Vin divided by re
D. Vin divided by re
20. The output voltage of an emitter follower is approximately
- 0
- VG
- Vin
- Vcc
C. Vin
21. The ac load line of an emitter follower is usually
- The same as the dc load line
- More horizontal than the dc load line
- Steeper than the dc load line
- Vertical
C. Steeper than the dc load line
22. If the input voltage to an emitter follower is too large, the output voltage will be
- Smaller
- Larger
- Equal
- Clipped
D. Clipped
23. If the Q point is at the middle of the dc load line, clipping will first occur on the
- Left voltage swing
- Upward current swing
- Positive half cycle of input
- Negative half cycle of input
D. Negative half cycle of input
24. If an emitter follower has VCEQ = 5 V, ICQ = 1 mA, and re = 1 kohm, the maximum peak-to-peak unclipped output is
- 1 V
- 2 V
- 5 V
- 10 V
B. 2 V
25. If the load resistance of an emitter follower is very large, the external ac emitter resistance equals
- Generator resistance
- Impedance of the base
- DC emitter resistance
- DC collector resistance
C. DC emitter resistance
26. If an emitter follower has re’ = 10 ohm and re = 90 ohm, the voltage gain is approximately
- 0
- 0.5
- 0.9
- 1
C. 0.9
27. A square wave out of an emitter follower implies
- No clipping
- Clipping at saturation
- Clipping at cutoff
- Clipping on both peaks
D. Clipping on both peaks
28. A Darlington transistor has
- A very low input impedance
- Three transistors
- A very high current gain
- One VBE drop
C. A very high current gain
29. The ac load line of the emitter follower is
- The same as the dc load line
- Different from the dc load line
- Horizontal
- Vertical
B. Different from the dc load line
30. If the generator voltage is 5 mV in an emitter follower, the output voltage across the load is closest to
- 5 mV
- 150 mV
- 0.25 V
- 0.5 V
A. 5 mV
31. If R1 is open in an emitter follower, which of these is true?
- DC base voltage is Vcc
- DC collector voltage is zero
- Output voltage is normal
- DC base voltage is zero
D. DC base voltage is zero
32. Usually, the distortion in an emitter follower is
- Very low
- Very high
- Large
- Not acceptable
A. Very low
33. The distortion in an emitter follower is
- Seldom low
- Often high
- Always low
- High when clipping occurs
D. High when clipping occurs
34. If a CE stage is direct coupled to an emitter follower, how many coupling capacitors are there between the two stages?
- 0
- 1
- 2
- 3
A. 0
35. A Darlington transistor has a Beta of 8000. If RE = 1 kohm and RL = 100 ohm, the input impedance of the base is closest to
- 8 kohm
- 80 kohm
- 800 kohm
- 8 Mohm
C. 800 kohm
36. The transistors of a class B push-pull emitter follower are biased at or near
- Cutoff
- The center of the dc load line
- Saturation
- The center of the ac load line
D. The center of the ac load line
37. Thermal runaway is
- Good for transistors
- Always desirable
- Useful at times
- Usually destructive
D. Usually destructive
38. The ac resistance of compensating diodes
- Must be included
- Is usually small enough to ignore
- Compensates for temperature changes
- Is very high
B. Is usually small enough to ignore
39. A small quiescent current is necessary with a class B push-pull amplifier to avoid
- Thermal runaway
- Destroying the compensating diodes
- Crossover distortion
- Excessive current drain
C. Crossover distortion
40. The zener current in a zener follower is
- Equal to the output current
- Smaller than the output current
- Larger than the output current
- Prone to thermal runaway
B. Smaller than the output current
41. In the two-transistor voltage regulator, the output voltage
- Is regulated
- Has much smaller ripple than the input voltage
- Is larger than the zener voltage
- All of the above
D. All of the above
42. For a class B push-pull emitter follower to work properly, the emitter diodes must
- Be able to control the quiescent current
- Have a power rating greater than the output power
- Have a voltage gain of I
- Match the compensating diodes
D. Match the compensating diodes
43. The maximum efficiency of a class B push-pull amplifier is
- 25 percent
- 50 percent
- 78.5 percent
- 100 percent
C. 78.5 percent
44. The ac emitter resistance of an emitter follower
- Equals the dc emitter resistance
- Is larger than the load resistance
- Has no effect on MPP
- Is usually less than the load resistance
D. Is usually less than the load resistance
