# MCQs in Bipolar Junction Transistor Amplifiers

(Last Updated On: December 8, 2017)

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 = Po / Pi?

• 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) re
• 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) re
• 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
• 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 ho?

• A) Volt
• B) Ohm
• C) Siemen
• D) No unit
13. Which of the h-parameters corresponds to re in a common-base configuration?
• A) hib
• B) hfb
• C) hrb
• D) hob
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) Ie
• B) Ic
• C) Ib
• 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 RC for a common-emitter fixed-bias configuration?
• A) ro ≥ 10RC
• B) ro < 10RC
• C) ro < ro
• D) ro > ro
19. Under which of the following condition(s) is the current gain Av ≈ β?
• A) ro ≥ 10RC
• B) RB ≥ 10re
• C) ro ≥ 10RC and RB ≥ 10re
• 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 Zo equal to RC?
• 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 –RC /re?
• 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) Ai
• B) Av
• C) Ap
• 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) βre > 10R2
• B) βRE > 10R2
• C) βRE < 10R2
• D) βre < 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 RL, 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 Rs and RL must be considered as a product.
• B) The effect of Rs and RL must be considered as a product and evaluated individually.
• C) The effect of Rs and RL 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) hi
• B) hr
• C) hf
• D) ho
39. In an unbypassed emitter bias configuration hie replaces _____ in the re model.
• A) re
• B) β
• C) βre
• D) Ib

### 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) re
• B) hybrid equivalent
• C) re 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) IC, IB
• B) IC, IE
• C) IB, IC
• D) None of the above

11. The level of re is determined by _____.

• A) α
• B) IE
• C) β
• D) IB
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) hi
• B) hr
• C) hf
• D) ho
15. For the common-emitter and common-base configurations, the magnitude of _____ and _____ is often not included in the model.
• A) hr, ho
• B) hi, he
• C) hi, hr
• D) he, ho
16. In a fixed-bias network, the input signal Vi is applied to the _____ of the transistor while the output Vo 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 Vb
• B) dc level of IB
• C) dc level of VB
• D) ac level of Ib
18. In a voltage-divider bias configuration, there can be a measurable difference in the results for _____ if the condition ro ≥ 10RC is not satisfied.
• A) Zo
• B) Av
• C) Ai
• 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 ro ≥ 10RE is not satisfied in the analysis of an emitter-follower configuration.
• A) Zi
• B) Zo
• C) Av
• D) Ai
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 RL, 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) βD
• 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 re in the hybrid equivalent circuit.
• A) hie
• B) hfe
• C) hre
• D) hoe
35. In a hybrid equivalent circuit, ______ is determined to make it easier to find the other parameters.
• A) Zi
• B) Zo
• C) Ai
• D) Av