Oscillator MCQs

16. An oscillator circuit using ideal op-amp and diodes is shown in the figure.

The time duration for positive part of the cycle is Δt1 and for negative part is Δt2. The value of \frac{Δt_1−Δt_2}{RC} will be _____________.

Answer
Answer. 1.2 to 1.3

17. Consider the oscillator circuit shown in the figure. The function of the network (shown in dotted lines) consisting of the 100 kΩ resistor in series with the two diodes connected back-to-back is to:

 

  1. introduce amplitude stabilization by preventing the op-amp from saturating and thus producing sinusoidal oscillations of fixed amplitude
  2. introduce amplitude stabilization by forcing the opamp to swing between positive and negative saturation and thus producing square wave oscillations of fixed amplitude
  3. introduce frequency stabilization by forcing the circuit to oscillate at a single frequency
  4. enable the loop gain to take on a value that produces square wave oscillations

Answer
Answer. a

18. An oscillator uses

  1. Positive feedback
  2. Negative feedback
  3. Both positive and negative feedback
  4. No feedback

Answer
Answer. a

19. One of the following oscillators contains the property of highly stable resonance characteristic. Identify the oscillator.

  1. Crystal
  2. Hartley
  3. Colpitts
  4. Wien bridge

Answer
Answer. a

20. One of the following is not a characteristic of an oscillator?

  1. Negative feedback
  2. Good output to input coupling
  3. Reasonably high transistor gain
  4. Alternating current signal output

Answer
Answer. a

21. Which among the following is the primary advantage of a crystal oscillator?

  1. Its frequency of oscillation remains almost constant.
  2. It can oscillate at any frequency.
  3. It gives a high output voltage.
  4. It operates on a very low dc supply voltage.

Answer
Answer. a

22. Among the following, identify the incorrect statement.

  1. An oscillator is a circuit that converts DC to AC.
  2. An oscillators generate sine wave.
  3. An oscillator is an amplifier that supplies its own input signal.
  4. In-phase feedback is called positive feedback.

Answer
Answer. b

23. An oscillator is an electronic device which converts

  1. Mechanical energy into electrical energy
  2. Electrical power into mechanical power
  3. DC power into AC power
  4. AC power into DC power and vice versa

Answer
Answer. c

24. Wein bridge oscillator uses

  1. RL circuit
  2. LC circuit
  3. RC circuit
  4. Crystal

Answer
Answer. c

25. The following oscillator is used at audio frequencies

  1. Colpitts’ oscillator
  2. Wien bridge oscillator
  3. Crystal oscillator
  4. None of the above

Answer
Answer. b

26. Crystal oscillator uses

  1. Silicon crystal
  2. Germanium crystal
  3. Crystal diode
  4. Piezo-electric quartz crystal

Answer
Answer. d

27. The most stable sine wave _________ with the most simple circuit is

  1. Colpitts
  2. Armstrong
  3. Phase-shift circuit
  4. Crystal

Answer
Answer. d

28. The Hartley law states that

  1. The maximum rate of information transmission depends on the channel bandwidth
  2. The maximum rate of information depends on the depth of modulation
  3. Redundancy is essential
  4. Only binary code may be used

Answer
Answer. a

29. A relaxation oscillator is one which

  1. Has two stable
  2. Has four stable states
  3. Relaxes indefinitely
  4. Produces non-sinusoidal output

Answer
Answer. d

30. The most stable sine wave oscillator with most simple circuit is

  1. Colpitts
  2. Armstrong
  3. Phase-shift circuit
  4. Crystal

Answer
Answer. d

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