Which of the following statements are correct?

(A) Zero crossing detector is a comparator with V_ref = 0

(B) An astable multivibrator is used to generate pulses of desired duration.

(C) The phase shift and wien bridge are commonly used sinewave oscillators for radio frequency.

(D) The frequency of a square wave generator is independant of trigger levels of comparator.

(E) A Triangular wave can be generated by integrating a square wave.

Choose the correct answer from the options given below:

Question

Question

This question was previously asked in

UGC NET Paper 2: Electronic Science 29 Oct 2022 Shift 1

Answer 1

The correct answer is option 3.

Schmitt trigger circuit

It is a positive feedback comparator circuit used to generate a square wave, also known as the square wave generator.
When the obtained square wave passes through an integrator, a triangular wave is obtained. Hence, statement E is true.
The frequency of a generated square wave depends upon the comparator's trigger levels, i.e. V_UT and V_LT. Hence, statement D is false.
V_UT and V_LT are known as the upper and lower threshold voltages.
When triggering voltages i.e. VUT and V_LT become zero, the Schmitt trigger is known as the zero crossing detector. Hence, statement A is true.

Astable multivibrator

It is also a positive feedback circuit that has no stable states.
Its output oscillates between two states hence it generates a only square wave of 50% duty cycle. Hence, statement C is false.

RC phase shift and Wien bridge oscillator

The phase shift and wien bridge are commonly used sinewave oscillators for audio frequency. Hence, statement B is false.