MCQs in Bipolar Junction Transistor Amplifiers

This is the Multiple Choice Questions in Bipolar Junction Transistor Amplifiers from the book Electronic Devices and Circuit Theory 10th Edition by Robert L. Boylestad. If you are looking for a reviewer in Electronics Engineering this will definitely help. I can assure you that this will be a great help in reviewing the book in preparation for your Board Exam. Make sure to familiarize each and every questions to increase the chance of passing the ECE Board Exam.

Online Questions and Answers 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

Practice Exam Test Questions

Choose the letter of the best answer in each questions.

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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credit: Robert L. Boylestad© 2014 www.PinoyBIX.org