Slew rate is the maximum rate of change of output voltage change with respect to time and is typically specified in units of volts per microsecond, V/µs. Op amps can enter a slew condition when a large, rapid moving signal is applied at the input. While slewing, the op amp enters an open loop condition and significant slew induced distortion can be seen on the output signal.

Equation 1 shows that the slew rate, SR, of an op amp is typically determined by the saturation current of the input stage, I_TAIL, and the compensation capacitor, C_C.

Slew rate typically scales with the quiescent current, I_Q, of the op amp. There are several ways that designers have overcome slew rate limitation. For example, lowering C_C, commonly known as decompensation, improves slew rate at the expense of stability. Decompensated op amps require a minimum gain and are not stable at unity gain. More commonly, modern op amps are equipped with slew boost technology that increases I_SAT to improve slew rate. Slew boost circuits can vary in implementation, but typically, expect about a four-fold improvement over comparable unboosted op amps.

The OPAx596 uses a proprietary design to achieve an unprecedented slew rate to I_Q ratio. The novel slew boost technology in OPAx596 provides a nearly 100 × slew rate improvement over comparable unboosted op amps. The op amp is unity gain stable and can be used configured as a buffer if desired.

Table 6-1 shows a comparison of slew rates and quiescent currents of different op amps.