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 Common-Collector Amplifier
• MCQs in The Common-Base Amplifier
• MCQs in Multistage Amplifiers
• MCQs in The Differential Amplifier
• MCQs in Common mode
• MCQs in CMRR (Common-mode rejection ratio)
• MCQs in Emitter-follower
• MCQs in AC Quantities

Begin and Good luck!

1. Which of the following techniques can be used in the sinusoidal ac analysis of transistor networks?

• A) Small-signal
• B) Large-signal
• C) Small- or large-signal
• D) None of the above

2. What is the limit of the efficiency defined by = P_o / P_i?

• A) Greater than 1
• B) Less than 1
• C) Always 1
• D) None of the above

3. Which of the following define(s) the conversion efficiency?

• A) Ac power to the load/ac input power
• B) Ac power to the load/dc power supplied
• C) Dc output power/ac input power
• D) All of the above

4. Which of the following should be done to obtain the ac equivalent of a network?

• A) Set all dc sources to zero
• B) Replace all capacitors by a short-circuit equivalent.
• C) Remove all elements bypassed by the short-circuit equivalent.
• D) All of the above

5. The _____ model suffers from being limited to a particular set of operating conditions if it is to be considered accurate.

• A) hybrid equivalent
• B) r_e
• C) β
• D) Thevenin

6. The _____ model fails to account for the output impedance level of the device and the feedback effect from output to input.

• A) hybrid equivalent
• B) r_e
• C) β
• D) Thevenin

7. Which of the following is (are) true regarding the input impedance for frequencies in the midrange ≤ 100 kHz of a BJT transistor amplifier?

• A) The input impedance is purely resistive.
• B) It varies from a few ohms to mega ohms.
• C) An ohmmeter cannot be used to measure the small-signal ac input impedance.
• D) All of the above

8. Which of the following is (are) true regarding the output impedance for frequencies in the midrange ≤ 100 kHz of a BJT transistor amplifier?

• A) The output impedance is purely resistive.
• B) It varies from a few ohms to more than 2 MΩ.
• C) An ohmmeter cannot be used to measure the small-signal ac output impedance.
• D) All of the above

9. What is the range of the current gain for BJT transistor amplifiers?

• A) less than 1
• B) 1 to 100
• C) above 100
• D) All of the above

10. The input impedance of a BJT amplifier is purely _____ in nature and can vary from a few _____ to _____.

• A) resistive, ohms, megohms
• B) capacitive, microfarads, farads
• C) inductive, millihenrys, henrys
• D) None of the above

11. For BJT amplifiers, the _____ gain typically ranges from a level just less than 1 to a level that may exceed 1000.

• A) voltage
• B) current
• C) impedance
• D) All of the above

12. What is the unit of the parameter h_o?

• A) Volt
• B) Ohm
• C) Siemen
• D) No unit

13. Which of the h-parameters corresponds to r_e in a common-base configuration?

• A) h_ib
• B) h_fb
• C) h_rb
• D) h_ob

14. What is the range of the input impedance of a common-base configuration?

• A) A few ohms to a maximum of 50 Ω
• B) 1 kΩ to 5 kΩ
• C) 100 kΩ to 500 kΩ
• D) 1 MΩ to 2 MΩ

15. What is the typical value of the current gain of a common-base configuration?

• A) Less than 1
• B) Between 1 and 50
• C) Between 100 and 200
• D) Undefined

16. What is the controlling current in a common-base configuration?

• A) I_e
• B) I_c
• C) I_b
• D) None of the above

17. What is the typical range of the output impedance of a common-emitter configuration?

• A) 10 Ω to 100 Ω
• B) 1 kΩ to 5 kΩ
• C) 40 kΩ to 50 kΩ
• D) 500 kΩ to 1 MΩ

18. Under which of the following conditions is the output impedance of the network approximately equal to R_C for a common-emitter fixed-bias configuration?

• A) r_o ≥ 10R_C
• B) r_o < 10R_C
• C) r_o < r_o
• D) r_o > r_o

19. Under which of the following condition(s) is the current gain Av ≈ β?

• A) r_o ≥ 10RC
• B) R_B ≥ 10r_e
• C) r_o ≥ 10R_C and R_B ≥ 10r_e
• D) None of the above

20. What does the negative sign in the voltage gain of the common-emitter fixed-bias configuration indicate?

• A) The output and input voltages are 180º out of phase.
• B) Gain is smaller than 1.
• C) Gain is larger than 1.
• D) None of the above

21. For the common-emitter fixed-bias configuration, there is a _____ phase shift between the input and output signals.

• A) 0º
• B) 45º
• C) 90º
• D) 180º

22. Which of the following configurations has an output impedance Z_o equal to R_C?

• A) Fixed-bias common-emitter
• B) Common-emitter voltage-divider with bypass capacitor
• C) Common-emitter voltage-divider without bypass capacitor
• D) All of the above

23. Which of the following configurations has a voltage gain of –R_C /r_e?

• A) Fixed-bias common-emitter
• B) Common-emitter voltage-divider with bypass capacitor
• C) Fixed-bias common-emitter and voltage-divider with bypass capacitor
• D) Common-emitter voltage-divider without bypass capacitor

24. Which of the following configurations has the lowest output impedance?

• A) Fixed-bias
• B) Voltage-divider
• C) Emitter-follower
• D) None of the above

25. The _____ configuration is frequently used for impedance matching.

• A) fixed-bias
• B) voltage-divider bias
• C) emitter-follower
• D) collector feedback

26. The emitter-follower configuration has a _____ impedance at the input and a _____ impedance at the output.

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

27. Which of the following gains is less than 1 for a common-base configuration?

• A) A_i
• B) A_v
• C) A_p
• D) None of the above

28. Which of the following conditions must be met to allow the use of the approximate approach in a voltage-divider bias configuration?

• A) βr_e > 10R₂
• B) βR_E > 10R2
• C) βR_E < 10R₂
• D) βr_e < 10R₂

29. Which one of the following configurations has the lowest input impedance?

• A) Fixed-bias
• B) Common-base
• C) Emitter-follower
• D) Voltage-divider?

30. For the collector dc feedback configuration, there is a _____ phase shift between the input and output signals.

• A) 0º
• B) 45º
• C) 90º
• D) 180º

31. Which of the following represent(s) the advantage(s) of the system approach over the r-model approach?

• A) Thevenin's theorem can be used.
• B) The effect of changing the load can be determined by a simple equation.
• C) There is no need to go back to the ac equivalent model and analyze the entire network.
• D) All of the above

32. The loaded voltage gain of an amplifier is always more than the no-load level.

• A) True
• B) False

33. The smaller the level of R_L, the larger the level of ac voltage gain.

• A) True
• B) False

34. Which of the following is (are) true to achieve a good overall voltage gain for the circuit?

• A) The effect of R_s and R_L must be considered as a product.
• B) The effect of R_s and R_L must be considered as a product and evaluated individually.
• C) The effect of R_s and R_L must be evaluated individually.
• D) None of the above

35. The _____ the source resistance and/or _____ the load resistance, the less the overall gain of an amplifier.

• A) smaller, smaller
• B) smaller, larger
• C) larger, smaller
• D) larger, larger

36. The current gain for the Darlington connection is _____.

• A) β₁ • (β₂/2)
• B) β₁ • β₂
• C) β₁ / β₂
• D) β1 • (β₂ – 1)

37. What is the voltage gain of a feedback pair connection?

• A) 1
• B) –1
• C) 100
• D) –100

38. Which of the following is referred to as the reverse transfer voltage ratio?

• A) h_i
• B) h_r
• C) h_f
• D) h_o

39. In an unbypassed emitter bias configuration h_ie replaces _____ in the r_e model.

• A) r_e
• B) β
• C) βr_e
• D) I_b

Fill-in-the-blanks Questions

1. The _____ of the input signal is one of the first concerns in the sinusoidal ac analysis of transistor networks.

• A) period
• B) frequency
• C) magnitude
• D) None of the above

2. The _____ model(s) is (are) commonly used in the small-signal ac analysis of transistor networks.

• A) r_e
• B) hybrid equivalent
• C) r_e and hybrid equivalent
• D) None of the above

3. The peak value of the ac input signal is controlled by the _____ in a transistor network for the frequencies in the low to midrange.

• A) resistors
• B) applied dc voltage
• C) capacitors
• D) None of the above

4. _____ can be applied to determine the response of the ac equivalent circuit.

• A) Mesh analysis
• B) Node analysis
• C) Thevenin's theorem
• D) All of the above

5. For transistor amplifiers, the no-load voltage gain is _____ the loaded voltage gain.

• A) smaller than
• B) greater than
• C) the same as
• D) None of the above

6. The input and output signals are _____ for the typical transistor amplifier at frequencies that permit ignoring the effects of the reactive elements.

• A) in phase
• B) 180º out of phase
• C) either in phase or 180º out of phase
• D) None of the above

7. One junction of an operating transistor is _____ and the other one is _____.

• A) forward-biased, forward-biased
• B) forward-biased, reverse-biased
• C) reverse-biased, reverse-biased
• D) None of the above

8. For a common-base configuration, the input impedance is relatively _____ and the output impedance quite _____.

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

9. The output voltage and the input voltage are _____ for the common-base configuration.

• A) 45º out of phase
• B) 90º out of phase
• C) 180º out of phase
• D) in phase

10. In a common-emitter configuration _____ is the controlling current while _____ is the controlled current.

• A) I_C, I_B
• B) I_C, I_E
• C) I_B, I_C
• D) None of the above

11. The level of re is determined by _____.

• A) α
• B) I_E
• C) β
• D) I_B

12. The output voltage and the input voltage are _____ for the common-emitter configuration.

• A) in phase
• B) 45º out of phase
• C) 90º out of phase
• D) 180º out of phase

13. The common-emitter configuration has a _____ level of input impedance with a _____ voltage and current gain.

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

14. _____ refers to the forward transfer current ratio.

• A) h_i
• B) h_r
• C) h_f
• D) h_o

15. For the common-emitter and common-base configurations, the magnitude of _____ and _____ is often not included in the model.

• A) h_r, h_o
• B) h_i, h_e
• C) h_i, h_r
• D) h_e, h_o

16. In a fixed-bias network, the input signal V_i is applied to the _____ of the transistor while the output V_o is off the _____.

• A) base, collector
• B) base, emitter
• C) emitter, collector
• D) None of the above

17. In a voltage-divider bias configuration, the voltage-divider equation is used to determine the _____.

• A) ac level of V_b
• B) dc level of I_B
• C) dc level of V_B
• D) ac level of I_b

18. In a voltage-divider bias configuration, there can be a measurable difference in the results for _____ if the condition r_o ≥ 10R_C is not satisfied.

• A) Z_o
• B) A_v
• C) A_i
• D) All of the above

19. The bypass capacitor in a common-emitter configuration _____ the voltage gain.

• A) significantly decreases
• B) significantly increases
• C) slightly increases
• D) slightly decreases

20. In an emitter-follower, the voltage gain is _____.

• A) slightly less than 1
• B) slightly more than 1
• C) a very large value
• D) None of the above

21. In an emitter-follower, the output voltage is _____ with the input voltage.

• A) 45º out of phase
• B) 90º out of phase
• C) 180º out of phase
• D) in phase

22. An emitter-follower has _____ impedance at the input and _____ impedance at the output.

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

23. _____ is slightly affected if the condition r_o ≥ 10R_E is not satisfied in the analysis of an emitter-follower configuration.

• A) Z_i
• B) Z_o
• C) A_v
• D) A_i

24. A common-base configuration has _____ impedance at the input and _____ impedance at the output.

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

25. In a common-base configuration, the input and output voltages are _____ and the output and input currents are _____.

• A) 180º out of phase, 180º out of phase
• B) 180º out of phase, in phase
• C) in phase,180º out of phase
• D) in phase, in phase

26. Ideally, the changes in the load resistor or the source resistor should have _____ effect on all the parameters of the two-port model.

• A) a great
• B) a moderate
• C) no
• D) None of the above

27. The loaded voltage gain of an amplifier is _____ the no-load level.

• A) always more than
• B) always less than
• C) always the same as
• D) None of the above

28. The coupling capacitor places the load and collector resistors in a _____ arrangement.

• A) series
• B) parallel
• C) series-parallel
• D) None of the above

29. The dc load line and ac load line both have the same _____ .

• A) x-intercept
• B) y-intercept
• C) slope
• D) Q-point

30. The _____ the level of R_L, the _____ the level of ac voltage gain.

• A) smaller, higher
• B) larger, lower
• C) smaller, lower
• D) None of the above

31. The _____ the source resistance, the _____ the overall gain of an amplifier.

• A) larger, higher
• B) larger, lower
• C) lower, lower
• D) None of the above

32. The ac voltage gain of a Darlington connection is about _____.

• A) 0
• B) 1
• C) β_D
• D) None of the above

33. The feedback pair uses a(n) _____ transistor driving a(n) _____ transistor, the two devices acting effectively much like one pnp transistor.

• A) pnp, npn
• B) pnp, pnp
• C) npn, npn
• D) None of the above

34. In an unbypassed emitter-bias configuration _____ replaces r_e in the hybrid equivalent circuit.

• A) h_ie
• B) h_fe
• C) h_re
• D) h_oe

35. In a hybrid equivalent circuit, ______ is determined to make it easier to find the other parameters.

• A) Z_i
• B) Z_o
• C) A_i
• D) A_v

 

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