Question

What is the use of the compensation capacitor in op-amp?

• A. Improves the amplification of op-amp
• B. Decreases the slew rate of op-amp
• C. Increases the bandwidth of op-amp
• D. Op-amp acts as all pass filter

Hint:

Op-Amp Compensation Purpose. Primarily for stability (preventing oscillations) in feedback configurations. Achieved by rolling off high-frequency gain. Consequences include reduced bandwidth and reduced slew rate.

Answer 1

The Correct Option is B

Frequency compensation in operational amplifiers, typically achieved using internal or external capacitors, is primarily implemented to ensure stability when negative feedback is applied
High-gain amplifiers can easily become unstable and oscillate at high frequencies without compensation
The compensation capacitor intentionally reduces the open-loop gain at higher frequencies, ensuring that the loop gain drops below unity before the phase shift reaches 180 degrees (preventing oscillation according to the Barkhausen criterion)
A major side effect of this necessary compensation is that it limits the internal charging currents, which in turn limits the maximum rate at which the output voltage can change
This maximum rate of change is the slew rate
Therefore, the compensation capacitor decreases the slew rate
It also decreases the bandwidth (gain-bandwidth product remains relatively constant)
It does not improve amplification (it reduces high-frequency gain) and does not make the op-amp an all-pass filter
While stability is the primary goal, decreasing the slew rate is a direct and significant consequence listed as an option