Define slew rate limiting and its effect on time-domain responses of op-amp circuits with large input steps.

• A. Slew rate is the maximum rate of change of the output; a large input step can cause a triangular waveform or slewing distortion.
• B. Slew rate is the maximum output voltage swing.
• C. Slew rate is the minimum input current required.
• D. Slew rate is unrelated to op-amps.

Answer: (A)

Slew rate is the maximum rate at which an op-amp’s output can change, usually expressed as dV/dt in V/µs. This limit comes from the finite current that charges and discharges the internal compensation capacitor, so the output cannot swing faster than that current-matter allows. When a large input step is applied, the ideal output would need a rapid, almost vertical change to reach the new value. If the required slope exceeds the op-amp’s slew rate, the output instead ramps at a constant maximum slope, producing a triangular-like transition and slewing distortion. This directly affects time-domain performance by delaying settling and distorting edges when handling large signals. For smaller, slower changes, the amplifier can follow normally within its bandwidth, and slewing isn’t encountered.