 # MCQs in BJT and FET Frequency Response

(Last Updated On: December 8, 2017)

This is the Multiple Choice Questions in BJT and FET Frequency Respons 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 Logarithms
• MCQs in Decibels
• MCQs in General Frequency Considerations
• MCQs in Low-frequency analysis – Bode Plot
• MCQs in Low-frequency response – BJT Amplifier
• MCQs in Low-frequency response – FET Amplifier
• MCQs in Miller Effect Capacitance
• MCQs in High-frequency response – BJT Amplifier
• MCQs in High-frequency response – FET Amplifier
• MCQs in Multistage Frequency Effects
• MCQs in Square wave testing
• MCQs in Computer Analysis

### Practice Exam Test Questions

Choose the letter of the best answer in each questions.

1. What is the ratio of the common logarithm of a number to its natural logarithm?

• a. 0.435
• b. 2
• c. 2.3
• d. 3.2

2. logea = _____ log10a

• a. 2.3
• b. 2.718
• c. e
• d. 1.414

3. By what factor does an audio level change if the power level changes from 4 W to 4096 W?

• a. 2
• b. 4
• c. 6
• d. 8

4. The input power to a device is 10,000 W at 1000 V. The output power is 500 W, and the output impedance is 100 Ω. Find the voltage gain in decibels.

• a. –30.01 dB
• b. –20.0 dB
• c. –13.01 dB
• d. –3.01 dB

5. What magnitude voltage gain corresponds to a decibel gain of 50?

• a. 31.6238
• b. 316.228
• c. 3162.38
• d. 31623.8

6. An amplifier rated at 30-W output is connected to a 5-Ω speaker. Calculate the input power required for full power output if the power gain is 20 dB.

• a. 3 mW
• b. 30 mW
• c. 300 mW
• d. 3 W

7. An amplifier rated at 30-W output is connected to a 5-Ω speaker. Calculate the input voltage for the rated output if the amplifier voltage gain is 20 dB.

• a. 1.225 mV
• b. 12.25 mV
• c. 122.5 mV
• d. 1.225 V

8. For audio systems, the reference level is generally accepted as

• a. 1 mW
• b. 1 W
• c. 10 mW
• d. 100 mW

9. For which of the following frequency region(s) can the coupling and bypass capacitors no longer be replaced by the short-circuit approximation?

• a. Low-frequency
• b. Mid-frequency
• c. High-frequency
• d. All of the above

10. By what other name(s) are the cut-off frequencies in a frequency response plot called?

• a. Corner frequency
• b. Break frequency
• c. Half-power frequency
• d. All of the above

11. What is the ratio of the output power to the input power at the cut-off frequencies in a normalized frequency response plot?

• a. 0.25
• b. 0.50
• c. 0.707
• d. 1

12. What is the ratio of the output voltage to the input voltage at the cut-off frequencies in a normalized frequency response plot?

• a. 0.25
• b. 0.50
• c. 0.707
• d. 1

13. What is the normalized gain expressed in dB for the cut-off frequencies?

• a. –3 dB
• b. +3 dB
• c. –6 dB
• d. –20 dB

14. The ________-frequency response of a transformer-coupled system is calculated primarily by the stray capacitance between the turns of the primary and secondary windings.

• a. Low
• b. Mid
• c. High

15. The larger capacitive elements of the design will determine the ________ cut-off frequency.

• a. Low
• b. Mid
• c. High

16. The smaller capacitive elements of the design will determine the ________ cut-off frequencies.

• a. Low
• b. Mid
• c. High

17. What is the ratio of the capacitive reactance XCS to the input resistance RI of the input RC circuit of a single-stage BJT amplifier at the low-frequency cut-off?

• a. 0.25
• b. 0.50
• c. 0.75
• d. 1.0

18. In the input RC circuit of a single-stage BJT, by how much does the base voltage lead the input voltage for frequencies much larger than the cut-off frequency in the low-frequency region?

• a. About 0º
• b. 45º
• c. About 90º
• d. None of the above

19. In the input RC circuit of a single-stage BJT, by how much does the base voltage lead the input voltage at the cut-off frequency in the low-frequency region?

• a. About 0º
• b. 45º
• c. About 90º
• d. None of the above

20. Determine the break frequency for this circuit. • a. 15.915 Hz
• b. 159.15 Hz
• c. 31.85 Hz
• d. 318.5 Hz

21. Refer to Figure 9.19. Calculate θ at 0.5f1.

• a. 63.43º
• b. 26.56º
• c. 45º
• d. Undefined

22. A change in frequency by a factor of ________ is equivalent to 1 octave.

• a. 2
• b. 10
• c. 5
• d. 20

23. A change in frequency by a factor of ________ is equivalent to 1 decade.

• a. 2
• b. 10
• c. 5
• d. 20

24. For the low-frequency response of a BJT amplifier, the maximum gain is where ________ .

• a. RB = 0 Ω
• b. RC = 0 Ω
• c. RE = 0 Ω

25. Which of the low-frequency cutoffs determined by CS, CC, or CE will be the predominant factor in determining the low-frequency response for the complete system?

• a. Lowest
• b. Middle
• c. Highest
• d. None of the above

26. Determine the lower cut-off frequency of this network.

• a. 15.8 Hz
• b. 46.13 Hz
• c. 238.73 Hz
• d. 1575.8 Hz

27. Which of the following elements is (are) important in determining the gain of the system in the high-frequency region?

• a. Interelectrode capacitances
• b. Wiring capacitances
• c. Miller effect capacitance
• d. All of the above

28. In the ________-frequency region, the capacitive elements of importance are the interelectrode (between terminals) capacitances internal to the active device and the wiring capacitance between the leads of the network.

• a. Low
• b. Mid
• c. High

29. Which of the following capacitors is (are) included in Ci for the high-frequency region of a BJT or FET amplifier?

30. In the hybrid or Giacoletto model, which one of the following does rb include?

• a. Base spreading resistance
• b. Base contact
• c. Base bulk
• d. All of the above

31. Which of the following configurations does (do) not involve the Miller effect capacitance?

• a. Common-emitter
• b. Common-base
• c. Common-collector
• d. All of the above

32. A 3-dB drop in hfe will occur at a frequency defined by ________.

33. What is the range of the capacitors Cgs and Cgd?

• a. 1 to 10 pF
• b. 1 to 10 nF
• c. 1 to 10 F
• d. 1 to 10 F

34. What is the range of the capacitor Cds?

• a. 0.01 to 0.1 pF
• b. 0.1 to 1 pF
• c. 0.1 to 1 nF
• d. 0.1 to 1 F

35. Which of the following statements is true for a square-wave signal?

• a. It is composed of both even and odd harmonics.
• b. It is composed only of odd harmonics.
• c. It is composed only of even harmonics.
• d. The harmonics waveforms are also square waves.

### FILL-IN-THE-BLANKS

1. Logarithms taken to the base _____ are referred to as common logarithms, while logarithms taken to the base _____ are referred to as natural logarithms.

• A. 10, e
• B e, 10
• C. 5, e
• D. 10, 5

2. The logarithm of a number _____ than 1 is always _____.

• A. greater, negative
• B. less, positive
• C. less, negative
• D. None of the above

3. The decibel (dB) is defined such that _____ decibel(s) = _____ bel(s).

• A. 1, 10
• B. 10, 1
• C. 1, 1
• D. 10, 10

4. The resistance associated with the 1-mW power level is _____ , chosen because it is the characteristic impedance of audio transmission lines.

• A. 100
• B. 250
• C. 400
• D. 600

5. The decibel gain of a cascaded system is the _____ of the decibel gains of each stage.

• A. sum
• B. difference
• C. product
• D. quotient

6. Voltage gains of _____ dB or higher should immediately be recognized as being quite high.

• A. 3
• B. 6
• C. 20
• D. 50

7. For the RC-coupled amplifier, the drop in gain at low frequencies is due to the increasing reactance of _____.

• A. CC
• B. Cs
• C. CE
• D. All of the above

8. To fix the frequency boundaries of relatively high gain, _____ was chosen to be the gain at the cut-off levels.

• A. 0.5Av mid
• B. 0.707Av mid
• C. Av low
• D. 0.5Av high

9. In the input RC circuit of a single-stage BJT or FET amplifier, as the frequency _____, the capacitive reactance _____ and _____ of the input voltage appears across the output terminals.

• A. increases, decreases, more
• B. increases, decreases, less
• C. increases, increases, more
• D. decreases, decreases, less

10. A change in frequency by a factor of 2 results in a _____ change in the ratio of the normalized gain.

• A. 3-dB
• B. 6-dB
• C. 10-dB
• D. 20-dB

11. A change in frequency by a factor of 10 results in a _____ change in the ratio of the normalized gain.

• A. 3-dB
• B. 6-dB
• C. 10-dB
• D. 20-dB

12. In the low-frequency region, the _____ low-frequency cut-off determined by CS, CC, or CE will have the greatest impact on the network.

• A. highest
• B. average
• C. lowest
• D. None of the above

13. The _____ region produces the maximum voltage gain in a single-stage BJT or FET amplifier.

• A. low-frequency
• B. mid-frequency
• C. high-frequency
• D. None of the above

14. For any inverting amplifier, the impedance capacitance will be _____ by a Miller effect capacitance sensitive to the gain of the amplifier and the interelectrode capacitance.

• A. unaffected
• B. increased
• C. decreased
• D. None of the above

15. The Miller effect is meaningful in the _____ amplifier.

• A. inverting
• B. noninverting
• C. inverting/noninverting
• D. None of the above

16. With a BJT amplifier in the high-frequency region, the capacitance Cbe is the _____ of the parasitic capacitances while Cce is the _____.

• A. smallest, largest
• B. largest, smallest
• C. smallest, medium
• D. None of the above

17. At very high frequencies, the effect of Ci is to _____ the total impedance of the parallel combination of R1, R2, R3, and Ci.

• A. increase
• B. maintain
• C. decrease
• D. None of the above

18. If the parasitic capacitors were the only elements to determine the high cut-off frequency, the _____ frequency would be the determining factor.

• A. lowest
• B. highest
• C. lowest or highest
• D. None of the above

19. The _____ configuration displays improved high-frequency characteristics over the _____ configuration.

• A. common-collector, common-emitter
• B. common-emitter, common-base
• C. common-emitter, common-collector
• D. common-base, common-emitter

20. The _____ of the upper cut-off frequencies defines a _____ possible bandwidth for a system.

• A. highest, maximum
• B. lowest, maximum
• C. lowest, minimum
• D. None of the above
• A. significantly smaller
• B. smaller
• C. significantly greater
• D. None of the above

22. For two identical stages in cascade, the drop-off rate in the high- and low-frequency regions has increased to _____ per decade.

• A. –3 dB
• B. –6 dB
• C. –20 dB
• D. –40 dB

23. The bandwidth _____ in a multistage amplifier compared to an identical single-stage amplifier.

• A. increases
• B. decreases
• C. remains the same
• D. None of the above

24. The _____ in the Fourier series has the same frequency as the square wave itself.

• A. fundamental
• B. third harmonic
• C. fifth harmonic
• D. seventh harmonic

25. The magnitude of the third harmonic is _____ of the magnitude of the fundamental.

• A. 1
• B. 0.5
• C. 0.33
• D. 0.25

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