Slew Rate, usually expressed in volts per microsecond (V/uSec), is a measure of the large signal frequency handling capability of an opamp. It's actually a limitation of the amount of current available to charge capacitances internal to the opamp.
The graphs for large signal handling capability you see in opamp datasheets are based on the opamp's ability to output an undistorted sine wave. But in synths we have signals like saw and pulse waveforms that should have very straight up and down slopes - which requires an even higher slew rate.
For example, to handle large audio signals (say 10v p-p) requires a minimum slew rate of about 1.5V/uSec. This rules out the 741 types that only have 0.5V/uSec. It's why the JFET input opamps like the TL07x or TL08x series are so popular for synth circuits - they have slew rates of around 13V/uSec. |