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