Bipolar Junction Transistor Amplifiers - MCQs

Multiple Choice Questions Topic Outline

• MCQs in BJT Amplifiers
• MCQs in Amplifier Operation
• MCQs in Transistor AC Models
• MCQs in The Common-Emitter Amplifier
• MCQs in The The Common-Collector Amplifier
• MCQs in The The Common-Base Amplifier
• MCQs in Multistage Amplifiers
• MCQs in The Differential Amplifier
• MCQs in GreenTech Application 6: Wind Power

Begin and Good luck!

1. For the common-emitter amplifier ac equivalent circuit, all capacitors are

• A) effectively shorts.
• B) effectively open circuits.
• C) not connected to ground.
• D) connected to ground.

2. For a common-emitter amplifier, the purpose of the emitter bypass capacitor is

• A) no purpose, since it is shorted out by R_E.
• B) to reduce noise.
• C) to despike the supply voltage.
• D) to maximize amplifier gain.

3. For a common-emitter amplifier, the purpose of swamping is

• A) to minimize gain.
• B) to reduce the effects of r'_e
• C) to maximize gain.
• D) no purpose.

4. An emitter-follower is also known as a

• A) common-emitter amplifier.
• B) common-base amplifier.
• C) common-collector amplifier.
• D) Darlington pair.

5. In a common-base amplifier, the input signal is connected to the

• A) base.
• B) collector.
• C) emitter.
• D) output.

6. The differential amplifier produces outputs that are

• A) common mode.
• B) in-phase with the input voltages.
• C) the sum of the two input voltages.
• D) the difference of the two input voltages.

7. The differential amplifier has

• A) one input and one output.
• B) two inputs and two outputs.
• C) two inputs and one output.
• D) one input and two outputs.

8. The dc emitter current of a transistor is 8 mA. What is the value of r_e?

• A) 320 Ω
• B) 13.3 kΩ
• C) 3.125 Ω
• D) 5.75 Ω

9. Refer to Figure 6-1. Calculate the value of V_B.

Figure 6-1

• A) 5 V
• B) 3.7 V
• C) 20 V
• D) 3 V

10. Refer to Figure 6-1. Find the value of I_E.

• A) 2 mA
• B) 4 mA
• C) 5 mA
• D) 6 mA

11. Refer to Figure 6-1. Determine the value of V_C.

• A) 20 V
• B) 10 V
• C) 5 V
• D) 0 V

12. Refer to Figure 6-1. Find the value of R_in(base).

• A) 420 Ω
• B) 50 kΩ
• C) 940 Ω
• D) 100.8 Ω

13. Refer to Figure 6-1. Calculate the value of R_in(tot).

• A) 37.7 kΩ
• B) 3.77 kΩ
• C) 378 Ω
• D) 2.25 kΩ

14. Refer to Figure 6-1. Determine the value of A_v.

• A) 49.6
• B) 5
• C) 100
• D) 595

15. Refer to Figure 6-1. If an emitter bypass capacitor was installed, determine the value of R_in(base).

• A) 416 Ω
• B) 5 kΩ
• C) 50 kΩ
• D) 500 Ω

16. Refer to Figure 6-1. If an emitter bypass capacitor was installed, calculate the value of R_in(tot).

• A) 378 Ω
• B) 420 Ω
• C) 500 Ω
• D) 40 k Ω

17. Refer to Figure 6-1. If an emitter bypass capacitor was installed, what would the new A_v be?

• A) 4.96
• B) 125
• C) 398
• D) 600

18. An emitter-follower amplifier has an input impedance of 107 kΩ. The input signal is 12 mV. The approximate output voltage is (common-collector)

• A) 8.92 V
• B) 112 mV
• C) 12 mV
• D) 8.9 mV

19. Refer to Figure 6-2. You notice while servicing this amplifier that the output signal at V_out is reduced from normal. The problem could be caused by

Figure 6-2

• A) an open C₃.
• B) an open C₂.
• C) an open base-emitter of Q₂.
• D) a shorted C₂.

20. Refer to Figure 6-2. The output signal from the first stage of this amplifier is 0 V. The trouble could be caused by

• A) an open C₄.
• B) an open C₂.
• C) an open base-emitter of Q₁.
• D) a shorted C₄.

21. A Darlington pair amplifier has

• A) high input impedance and high voltage gain.
• B) low input impedance and low voltage gain.
• C) a voltage gain of about 1 and a low input impedance.
• D) a low voltage gain and a high input impedance.

22. You have a need to apply an amplifier with a very high power gain. Which of the following would you choose?

• A) common-collector
• B) common-base
• C) common-emitter
• D) emitter-follower

23. What is the most important r parameter for amplifier analysis?

• A) r_b′
• B) r_c′
• C) r_e′
• D) none of the above

24. A common-emitter amplifier has _____ voltage gain, _____ current gain, _____ power gain, and _____ input impedance.

• A) high, low, high, low
• B) high, high, high, low
• C) high, high, high, high
• D) low, low, low, high

25. To analyze the common-emitter amplifier, what must be done to determine the dc equivalent circuit?

• A) leave circuit unchanged
• B) replace coupling and bypass capacitors with opens
• C) replace coupling and bypass capacitors with shorts
• D) replace V_CC with ground

26. When the bypass capacitor is removed from a common-emitter amplifier, the voltage gain

• A) increases.
• B) decreases.
• C) has very little effect.

27. A common-collector amplifier has _____ input resistance, _____ current gain, and _____ voltage gain.

• A) high, high, low
• B) high, low, low
• C) high, low, high

28. A Darlington pair provides beta _____ for _____ input resistance.

• A) multiplication, decreased
• B) multiplication, increased
• C) division, decreased

29. The total gain of a multistage amplifier is the _____.

• A) sum of individual voltage gains
• B) sum of dB voltage gains
• C) none of the above

30. What is r_e equal to in terms of h parameters?

• A) h_re / h_oe
• B) (h_re + 1) / h_oe
• C) h_ie – (h_re / h_oe)(1 + h_fe)
• D) h_fe
• E) none of the above

31. The advantage that a Sziklai pair has over a Darlington pair is

• A) higher current gain.
• B) less input voltage is needed to turn it on.
• C) higher input impedance.
• D) higher voltage gain.

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• Floyd’s Electronic Devices  (Chapter Quiz)

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