ObjectiveMcq
Print Protected
This page is protected for print. Use the website to view the content.
Conditions which are required to be satisfied to operate the circuit as an oscillator are called as _______________ for sustained oscillations.
Correct Answer: D — Barkhausen criterion
The correct answer is D: Barkhausen Criterion.
The Barkhausen criterion is the set of conditions a circuit must satisfy to function as an oscillator and produce sustained oscillations without any external input signal.
Two conditions must be met simultaneously:
Loop gain condition: The total loop gain must equal unity — |Aβ| = 1, where A is the amplifier gain and β is the feedback factor.
Phase shift condition: The total phase shift around the closed loop must be 0° or an integer multiple of 360°, ensuring the feedback signal is in phase with the input.
Working Principle:
An amplifier is coupled with a feedback network.
The amplifier amplifies the signal; the feedback network returns a portion of the output to the input.
If |Aβ| > 1: oscillations grow until the system saturates.
If |Aβ| < 1: oscillations die out.
Only when |Aβ| = 1 and the phase condition is met do oscillations sustain indefinitely.
Applications:
Signal generators producing sinusoidal, square, or triangular waveforms.
RF circuits for generating carrier signals in communication systems.
Frequency generation and modulation circuits.
Limitation: The criterion does not account for real-world non-idealities such as component tolerances, temperature variations, frequency drift, or distortion.