Q. Can you explain about Slew Rate?

Slew (or slewing) rate is a measure of how fast the output voltage can change. It is given by the maximum value of dvo/dt , which is normally measured in response to a large input voltage step

and is therefore usually associated with low closed-loop voltage gain. For a 741 the slew rate is 0.5 V/µsat A = 1. For more recently developed op amps, the slew rate ranges from 5 to 100 V/µs. The effect of the slew rate in response to an input step voltage is shown in Figure. If one attempts to make the output voltage change faster than the slew rate, nonlinearity will be introduced. When specifying such output voltage requirements as rise time, output voltage, and frequency, it is necessary to choose an op amp with a slew rate that meets the specifications.With a sine-wave input, the slew rate limits a combination of maximum operating frequency and output voltage magnitude.

The slew rate occurs because at some stage in the amplifier a frequency-compensating capacitor will have to be charged, and the available limited charging current restricts themaximum rate of change of the capacitor voltage. With externally compensated op amps, such as the 709, slew rates will depend on the value of the compensating capacitors, which are in turn chosen on the basis of the closed-loop gain needed. The lower the gain, the higher the compensating capacitors, and hence the lower the slew rate. For a µA 709, the slew rate is 0.3 V/µsat A = 1 and 1.5 V/µsat A = 10.