 # MCQs in DC Biasing – BJTs

(Last Updated On: December 8, 2017)

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)    IB and IC
• B)    IE and IC
• C)    IB and IE
• D)    IB, IC, and IE

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

• A)    IC and IE
• B)    IC and IB
• C)    IE and IB
• 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 IB _____ 0 A.

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

6. The saturation region is defined by VCE _____ VCEsat.

• 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)    VBE
• B)    VCE
• C)    VBC
• 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 VCC = 20 V, RC = 5 kΩ, and IC = 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)    IB is essentially zero amperes.
• B)    R1 and R2 are considered to be series elements.
• C)    βRE ≥ 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 VCEQ. • A)    8.78 V
• B)    0 V
• C)    7.86 V
• D)    18 V

16. Calculate ICsat. • A)    35.29 mA
• B)    5.45 mA
• C)    1.86 mA
• D)    4.72 mA

17. Calculate VCE. • A) 4.52 V
• B) –4.52 V
• C) 4.48 V
• D) –4.48 V

18. Calculate VCE. • 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 VCB and IB 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 ETh for this network. • A) −12.12 V
• B) 16.35 V
• C) −3.65 V
• D) 10 V

22. Calculate Rsat if VCE = 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 VE = 0.1·VCC in order to calculate RC and RE. • 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 toff is 56 ns, tf = 14 ns, and tr = 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 ton and defined as the delay time plus the time element.

• A) True
• B) False

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

• A) True
• B) False

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

• A) 10, 60
• B) 25, 75
• C) 40, 90

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

• A) S(ICO)
• B) S(VBE)
• 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(ICO)
• B) S(VBE)
• 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(ICO)
• B) S(VBE)
• C) S(β)
• D) Undefined

33. Use this table to determine the change in IC from 25ºC to 175ºC for RB / RE = 250 due to the S(ICO) 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 RB = 240 kΩ and β = 100 due to the S(VBE) stability factor. • A) 145.8 µA
• B) 145.8 nA
• C) –145.8 µA
• D) –145.8 nA

35. Determine ICQ at a temperature of 175º C if ICQ = 2 mA at 25º C for RB / RE = 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 VCC’ 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 ICEO
• C) both current gain β and leakage current ICEO
• 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) RB
• B) RC
• C) β
• D) RB and β

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

• A) minimum, left of the VCEsat line
• B) minimum, right of the VCEsat line
• C) maximum, left of the VCEsat line
• D) maximum, right of the VCEsat 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) RB
• B) RC
• C) VCC
• D) VBE

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

• A) RB
• B) RC
• C) VCC
• D) IB

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 ETh
• B) Thevenin resistance RTh
• C) Base voltage VB
• D) RC

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 RC’

• 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) IC’ IC
• B) IB + IC’ IC
• C) IB’, IC
• 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, VCE is usually about _____ % to _____ % of VCC’

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

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

• A) β
• B) VBE
• C) ICO
• D) All of the above

22. As the temperature increases, β _____, VBE _____, and ICO _____ 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 IB 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 RE’, 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