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Comparators & Waveform Generators MCQs

Practice Comparators & Waveform Generators MCQs with four options, answers and explanations for focused Electronics & Telecommunication Engineering revision.

Question 2
Analog ElectronicsComparators & Waveform Generators

A zero-crossing detector is essentially a comparator whose reference voltage is?

  • A0 V
  • B1 V
  • CEqual to the positive supply
  • DAlways equal to the output
Report an error
Correct Answer: A. 0 V
Explanation: A zero-crossing detector compares the input with a zero-volt reference and switches output polarity when the input crosses zero.
Reference: Standard analog electronics: zero-crossing detector
Question 3
Analog ElectronicsComparators & Waveform Generators

An op-amp relaxation oscillator typically generates a square wave by combining a Schmitt-trigger action with?

  • ARC charging and discharging
  • BA transformer rectifier only
  • CA current mirror with no capacitor
  • DA crystal operated only at series resonance
Report an error
Correct Answer: A. RC charging and discharging
Explanation: The capacitor repeatedly charges and discharges between hysteresis thresholds, causing the comparator output to switch and sustain oscillation.
Reference: Standard analog electronics: relaxation oscillator
Question 4
Analog ElectronicsComparators & Waveform Generators

In a basic op-amp astable relaxation oscillator, increasing the timing resistance while all other parameters remain unchanged generally causes the oscillation frequency to?

  • AIncrease
  • BDecrease
  • CRemain exactly unchanged
  • DBecome infinite
Report an error
Correct Answer: B. Decrease
Explanation: Increasing timing resistance increases the RC charging/discharging time, so the oscillation period grows and frequency decreases.
Reference: Standard analog electronics: relaxation oscillator timing