- 2072 Kartik · 3 marks
Short note: CMRR, PSRR and slew rate
Short answer
CMRR is the ratio of differential gain to common-mode gain, expressed in dB. PSRR is the change in input offset voltage per unit supply voltage change (µV/V); smaller is better. Slew rate is the maximum rate of change of output voltage, dVo/dt in V/µs.
Define the terms CMRR, PMRR (PSRR) and Slew Rate.
- CMRR (common-mode rejection ratio): the ratio of differential gain to common-mode gain, CMRR = |Ad/Acm|, usually in dB: CMRR = 20 log10|Ad/Acm|. It shows how well the op-amp rejects signals (noise, hum) common to both inputs. For the 741 it is about 90 dB; ideal is infinite.
- PSRR (power supply rejection ratio, also SVRR): the change in input offset voltage per unit change in one supply voltage, the other supply being constant: PSRR = ΔVio/ΔV, in µV/V (or dB). It shows how well the op-amp rejects supply ripple and variation. For the 741 it is 30 µV/V typical; smaller is better.
- Slew rate (SR): the maximum rate of change of output voltage, SR = (dVo/dt)max, in V/µs. It is set by the current charging the internal compensation capacitor (SR = Imax/C). For the 741 it is 0.5 V/µs. A sine output of peak Vm is undistorted only up to fmax = SR/(2πVm).
✓ Answer checked by Claude Opus 5.5 (high effort)
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