 Oscillators MCQS – N4notes

# Oscillators MCQS

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

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

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. 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.

4. 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

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. Calculate the fr of a lead-lag network if R1 = R2 = 6.8 kΩ, and C1 = C2 = 0.05 µF.

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

8. 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.

9. 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.

10. Sinusoidal oscillators operate with _____ feedback.

• A. positive
• B. negative

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

• A. 0
• B. 90
• C. 180
• D. 45

12. 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.

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

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

14. 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

15. 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.

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

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

17. 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
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18. 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

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

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