MCQs in DC Biasing - BJTs

This is the Multiple Choice Questions in DC Biasing - BJTs 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 Operating Point
• MCQs in Fixed-Bias Circuit
• MCQs in Emitter-Stabilized Bias Circuit
• MCQs in Voltage-Divider Bias
• MCQs in DC Bias with Voltage Feedback
• MCQs in Miscellaneous Bias Configurations
• MCQs in Design Operations
• MCQs in Transistor Switching Networks
• MCQs in Troubleshooting Techniques
• MCQs in PNP Transistors
• MCQs in Bias Stabilization

Practice Exam Test Questions

Choose the letter of the best answer in each questions.

1. Which of the following currents is nearly equal to each other?

• A)    I_B and I_C
• B)    I_E and I_C
• C)    I_B and I_E
• D)    I_B, I_C, and I_E

2. The ratio of which two currents is represented by β?

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

3. At what region of operation is the base-emitter junction forward biased and the base-collector junction reverse biased?

• A)    Saturation
• B)    Linear or active
• C)    Cutoff
• D)    None of the above

4. Calculate the approximate value of the maximum power rating for the transistor represented by the output characteristics of Figure 4.1?

• A)    250 mW
• B)    170 mW
• C)    50 mW
• D)    0 mW

5. The cutoff region is defined by I_B _____ 0 A.

• A)    >
• B)    <
• C)    ≤
• D)    ≥

6. The saturation region is defined by V_CE _____ V_CEsat.

• A)    >
• B)    <
• C)    ≤
• D)    ≥

7. For the BJT to operate in the active (linear) region, the base-emitter junction must be _____-biased and the base-collector junction must be _____-biased.

• A)    forward, forward
• B)    forward, reverse
• C)    reverse, reverse
• D)    reverse, forward

8. For the BJT to operate in the saturation region, the base-emitter junction must be _____-biased and the base-collector junction must be _____-biased.

• A)    forward, forward
• B)    forward, reverse
• C)    reverse, reverse
• D)    reverse, forward

9. Which of the following voltages must have a negative level (value) in any npn bias circuit?

• A)    V_BE
• B)    V_CE
• C)    V_BC
• D)    None of the above

10. For what value of β does the transistor enter the saturation region?

• A)    20
• B)    50
• C)    75
• D)    116

11. Determine the reading on the meter when V_CC = 20 V, R_C = 5 kΩ, and I_C = 2 mA.

• A)    10 V
• B)    –10 V
• C)    0.7 V
• D)    20 V

12. Which of the following is assumed in the approximate analysis of a voltage divider circuit?

• A)    I_B is essentially zero amperes.
• B)    R₁ and R₂ are considered to be series elements.
• C)    β_RE ≥ 10R₂
• D)    All of the above

13. It is desirable to design a bias circuit that is independent of the transistor beta.

• A)    True
• B)    False

14. Calculate the voltage across the 91 kΩ resistor.

• A)    18 V
• B)    9.22 V
• C)    3.23 V
• D)    None of the above

15. Calculate the value of V_CEQ.

• A)    8.78 V
• B)    0 V
• C)    7.86 V
• D)    18 V

16. Calculate I_Csat.

• A)    35.29 mA
• B)    5.45 mA
• C)    1.86 mA
• D)    4.72 mA

17. Calculate V_CE.

• A) 4.52 V
• B) –4.52 V
• C) 4.48 V
• D) –4.48 V

18. Calculate V_CE.

• A) –4.52 V
• B) 4.52 V
• C) –9 V
• D) 9 V

19. Which of the following is (are) related to an emitter-follower configuration?

• A) The input and output signals are in phase.
• B) The voltage gain is slightly less than 1.
• C) Output is drawn from the emitter terminal.
• D) All of the above

20. Determine the values of V_CB and I_B for this circuit.

• A) 1.4 V, 59.7 µA
• B) –1.4 V, 59.7 µA
• C) –9.3 V, 3.58 µA
• D) 9.3 V, 3.58 µA

21. Calculate E_Th for this network.

• A) −12.12 V
• B) 16.35 V
• C) −3.65 V
• D) 10 V

22. Calculate Rsat if V_CE = 0.3 V.

• A) 49.2 Ω
• B) 49.2 kΩ
• C) 49.2 mΩ
• D) 49.2 MΩ

23. You can select the values for the emitter and collector resistors from the information that is provided for this circuit.

• A) True
• B) False

24. In the case of this circuit, you must assume that V_E = 0.1·V_CC in order to calculate R_C and R_E.

• A) True
• B) False

25. Which of the following is (are) the application(s) of a transistor?

• A) Amplification of signal
• B) Switching and control
• C) Computer logic circuitry
• D) All of the above

26. Calculate the storage time in a transistor switching network if t_off is 56 ns, t_f = 14 ns, and t_r = 20 ns.

• A) 70 ns
• B) 42 ns
• C) 36 ns
• D) 34 ns

27. The total time required for the transistor to switch from the "off" to the "on" state is designated as t_on and defined as the delay time plus the time element.

• A) True
• B) False

28. For an "on" transistor, the voltage V_BE should be in the neighborhood of 0.7 V.

• A) True
• B) False

29. For the typical transistor amplifier in the active region, V_CE is usually about _____ % to _____ % of V_CC.

• A) 10, 60
• B) 25, 75
• C) 40, 90

30. Which of the following is (are) a stability factor?

• A) S(I_CO)
• B) S(V_BE)
• C) S(β)
• D) All of the above

31. In a fixed-bias circuit, which one of the stability factors overrides the other factors?

• A) S(I_CO)
• B) S(V_BE)
• C) S(β)
• D) Undefined

32. In a voltage-divider circuit, which one of the stability factors has the least effect on the device at very high temperature?

• A) S(I_CO)
• B) S(V_BE)
• C) S(β)
• D) Undefined

33. Use this table to determine the change in I_C from 25ºC to 175ºC for R_B / R_E = 250 due to the S(I_CO) stability factor. Assume an emitter-bias configuration.

• A) 140.34 nA
• B) 140.34 µA
• C) 42.53 nA
• D) 0.14034 nA

34. Determine the change in IC from 25ºC to 175ºC for the transistor defined in this table for fixed-bias with R_B = 240 kΩ and β = 100 due to the S(V_BE) stability factor.

• A) 145.8 µA
• B) 145.8 nA
• C) –145.8 µA
• D) –145.8 nA

35. Determine I_CQ at a temperature of 175º C if I_CQ = 2 mA at 25º C for R_B / R_E = 20 due to the S(β) stability factor.

• A) 2.417 mA
• B) 2.392 mA
• C) 2.25 mA
• D) 2.58 mA

Fill-in-the-blanks Questions

1. By definition, quiescent means _____.

• A) quiet
• B) still
• C) inactive
• D) All of the above

2. _____ should be considered in the analysis or design of any electronic amplifiers.

• A) dc
• B) ac
• C) dc and ac
• D) None of the above

3. For the dc analysis the network can be isolated from the indicated ac levels by replacing the capacitor with _____.

• A) an open circuit equivalent
• B) a short circuit equivalent
• C) a source voltage
• D) None of the above

4. In a fixed-bias circuit with a fixed supply voltage V_CC’ the selection of a _____ resistor sets the level of _____ current for the operating point.

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

5. Changes in temperature will affect the level of _____.

• A) current gain β
• B) leakage current I_CEO
• C) both current gain β and leakage current I_CEO
• D) None of the above

6. In a fixed-bias circuit, the magnitude of IC is controlled by and therefore is a function of _____.

• A) R_B
• B) R_C
• C) β
• D) R_B and β

7. For a transistor operating in the saturation region, the collector current I_C is at its _____ and the collector-emitter voltage V_CE is to the _____.

• A) minimum, left of the V_CEsat line
• B) minimum, right of the V_CEsat line
• C) maximum, left of the V_CEsat line
• D) maximum, right of the V_CEsat line

8. The dc load line is determined solely by the _____.

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

9. A change in value of _____ will create a new load line parallel to its previous one in a fixed-bias circuit.

• A) R_B
• B) R_C
• C) V_CC
• D) V_BE

10. In a fixed-bias circuit, the slope of the dc load line is controlled by _____.

• A) R_B
• B) R_C
• C) V_CC
• D) I_B

11. The emitter resistor in an emitter-stabilized bias circuit appears to be _____ in the base circuit.

• A) larger
• B) smaller
• C) the same
• D) None of the above

12. _____is the primary difference between the exact and approximate techniques used in the analysis of a voltage divider circuit.

• A) Thevenin voltage E_Th
• B) Thevenin resistance R_Th
• C) Base voltage V_B
• D) R_C

13. The Thevenin equivalent network is used in the analysis of the _____ circuit.

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

14. The saturation current of a transistor used in a fixed-bias circuit is _____ its value used in an emitter-stabilized or voltage-divider bias circuit for the same values of R_C’

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

15. In a collector feedback bias circuit, the current through the collector resistor is _____ and the collector current is _____.

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

16. _____is the least stabilized circuit.

• A) Fixed bias
• B) Emitter-stabilized bias
• C) Voltage divider
• D) Voltage feedback

17. _____ is less dependent on the transistor beta.

• A) Fixed bias
• B) Emitter bias
• C) Voltage divider
• D) Voltage feedback

18. In a transistor-switching network, the level of the resistance between the collector and emitter is _____ at the saturation and is _____at the cutoff.

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

19. In a transistor-switching network, the operating point switches from _____ to _____ regions along the load line.

• A) cutoff, active
• B) cutoff, saturation
• C) active, saturation
• D) None of the above

20. For the typical transistor amplifier in the active region, V_CE is usually about _____ % to _____ % of V_CC’

• A) 0, 100
• B) 25, 75
• C) 45, 55
• D) None of the above

21. In any amplifier employing a transistor, the collector current I_C is sensitive to _____.

• A) β
• B) V_BE
• C) I_CO
• D) All of the above

22. As the temperature increases, β _____, V_BE _____, and I_CO _____ in value for every 10ºC.

• A) increases, decreases, doubles
• B) decreases, increases, remains the same
• C) decreases, increases, doubles
• D) increases, increases, triples

23. A significant increase in leakage current due to increase in temperature creates _____between I_B curves.

• A) smaller spacing
• B) larger spacing
• C) the same space as at lower temperature
• D) None of the above

24. The _____the stability factor, the _____sensitive the network is to variations in that parameter.

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

25. In an emitter-bias configuration, the _____ the resistance R_E’, the _____ the stability factor, and the _____ stable is the system.

• A) smaller, lower, less
• B) larger, more, more
• C) smaller, more, more
• D) larger, lower, more

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Answer in DC Biasing - BJTs

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