# MCQs in Oscillators

MCQs in Oscillators from the book Electronic Devices - Electron Flow Version and Conventional Current Version 8th Edition by Thomas L. Floyd.

This is the Multiple Choice Questions in Oscillators from the book Electronic Devices - Electron Flow Version and Conventional Current Version 8th Edition by Thomas L. Floyd. 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.

### Practice Exam Test Questions

Choose the letter of the best answer in each questions.

1. In order to start up, a feedback oscillator requires

• A. negative feedback less than 1.
• B. positive feedback greater than 1.
• C. unity feedback equal to 1.
• D. no feedback.

2. What is the total phase shift requirement, around the feedback loop, for a phase-shift oscillator?

• A. 90°
• B. 180°
• C. 270°
• D. 360°

3. What is the relationship between the series and parallel resonant frequencies of a quartz crystal?

• A. They are equal.
• B. Parallel resonant frequency is approximately 1 kHz higher than series resonant frequency.
• C. Series resonant frequency is approximately 1 kHz higher than parallel resonant frequency.
• D. none of the above

4. At series resonance, the impedance of a crystal is

• A. minimum.
• B. maximum.
• C. equal.
• D. zero.

5. At parallel resonance, the impedance of a crystal is

• A. minimum.
• B. maximum.
• C. equal.
• D. zero.

6. What is the minimum frequency at which a crystal will oscillate?

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

7. Refer to Figure 16-1(a). This circuit is known as

Figure 16-1

• A. a Clapp oscillator.
• B. an Armstrong oscillator.
• C. a Colpitts oscillator.
• D. a Hartley oscillator.

8. Refer to Figure 16-1(b). This circuit is known as

• A. a Clapp oscillator.
• B. an Armstrong oscillator.
• C. a Colpitts oscillator.
• D. a Hartley oscillator.

9. Refer to Figure 16-1(c). This circuit is known as

• A. a Clapp oscillator.
• B. an Armstrong oscillator.
• C. a Colpitts oscillator.
• D. a Hartley oscillator.

10. Refer to Figure 16-1(b). The resonant frequency is controlled by

• A. C3 and L1.
• B. C2, C4, C5, and L1.
• C. C3, C4, C5, and L1.
• D. C3, C4, C5, and L2.

11. Calculate the fr of a lead-lag network if R1 = R2 = 6.8 kâ„¦, and C1 = C2 = 0.05 ÂµF.

• A. 468 Hz
• B. 4.68 kHz
• C. 46.8 kHz
• D. 468 kHz

12. Refer to Figure 16-2. Calculate the resonant frequency.

Figure 16-2

• A. 1.126 kHz
• B. 6.17 kHz
• C. 23.9 MHz
• D. 14.1 MHz

13. Refer to Figure 16-3. Determine the resonant frequency.

Figure 16-3

• A. 123.4 kHz
• B. 61.7 kHz
• C. 45.94 kHz
• D. 23.1 kHz

14. Refer to Figure 16-3. If C1 increases in value, the resonant frequency will

• A. increase.
• B. decrease.
• C. remain the same.
• D. none of the above

15. A certain oscillator has a tap on the inductor in the tank circuit. This oscillator is probably

• A. a Colpitts oscillator.
• B. a Clapp oscillator.
• C. a crystal oscillator.
• D. a Hartley oscillator.

16. An op-amp integrator has a square-wave input. The output should be

• A. a sine wave.
• B. a triangle wave.
• C. a square wave.
• D. pure dc.

17. Refer to Figure 16-4. This circuit is

Figure 16-4

• A. a sine-wave oscillator.
• B. a monostable multivibrator.
• C. an astable multivibrator.
• D. a VCO.

18. Refer to Figure 16-4. Determine the frequency of oscillation, if any.

• A. 131 Hz
• B. 262 Hz
• C. 2.62 kHz
• D. none

19. Refer to Figure 16-4. What is the duty cycle, if any?

• A. 16.3%
• B. 54.5%
• C. 86.9%
• D. none

20. Refer to Figure 16-4. Assuming it is configured as an oscillator and if you desired to reduce the duty to less than 50%, the following circuit change would need to be made.

• A. Reduce the size of R1.
• B. Reduce the size of R2.
• C. Increase the size of R1.
• D. Connect a diode in parallel with R1.

21. A circuit that can change the frequency of oscillation with an application of a dc voltage is sometimes called

• A. a voltage-controlled oscillator.
• B. a crystal oscillator.
• C. a Hartley oscillator.
• D. an astable multivibrator.

22. Sinusoidal oscillators operate with _____ feedback.

• A. positive
• B. negative

23. One condition for positive feedback is that the phase shift around the feedback loop must be _____°.

• A. 0
• B. 90
• C. 180
• D. 45

24. The start-up gain of an oscillator must be _____ one.

• A. equal to
• B. less than
• C. greater than
• D. none of the above

25. For frequencies up to 1 MHz, the _____ is the most widely used type of sinusoidal RC oscillator.

• A. Wien-bridge
• B. phase-shift
• C. twin-T
• D. none of the above

26. The lead-lag circuit in the Wien-bridge oscillator has a resonant frequency at which the attenuation is

• A. 1/2.
• B. 1/4.
• C. 1/3.
• D. 1/5.

27. The attenuation of the three-section RC feedback phase-shift oscillator is

• A. 1/9.
• B. 1/30.
• C. 1/3.
• D. 1/29.

28. The twin-T oscillator produces a _____ response.

• A. low-pass
• B. high-pass
• C. band-pass
• D. band-stop

29. The feedback signal in a(n) _____ oscillator is derived from a capacitive voltage divider in the LC circuit.

• A. Hartley
• B. Armstrong
• C. Colpitts
• D. none of the above

30. The feedback signal in a(n) _____ oscillator is derived from an inductive voltage divider in the LC circuit.

• A. Hartley
• B. Armstrong
• C. Colpitts
• D. none of the above

#### TRUE/FALSE

1. Oscillators operate on negative feedback.

• A. True
• B. False

2. The start-up gain of an oscillator must be greater than 1.

• A. True
• B. False

3. The feedback signal in a Hartley oscillator is derived from an inductive voltage in the tank circuit.

• A. True
• B. False

4. Crystal oscillators are inherently unstable.

• A. True
• B. False

5. The frequency in a VCO can be varied with a DC voltage.

• A. True
• B. False

6. LC feedback elements are normally used in oscillators for frequencies greater than 1 MHz.

• A. True
• B. False

7. The positive feedback voltage in an oscillator has no net phase shift.

• A. True
• B. False

8. For a Wien-bridge oscillator, resonance occurs when Vout/Vin = 1.

• A. True
• B. False

9. The feedback network in a Colpitts oscillator contains two series capacitors and a parallel inductor.

• A. True
• B. False

10. In the astable mode, a 555 timer is connected as a free-running relaxation oscillator.

• A. True
• B. False

### Complete List of Chapter MCQs in Floyd's Electronic Devices

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