Cload for OPA454

Hi y.i.

The concern when driving a capacitive load (Cload) with an op amp is the ability for the circuit to have good transient response and remain stable. The circuit configuration, inverting or non-inverting, and the closed-loop gain being used are factors in how large of a Cload the op amp will drive. You can see when comparing OPA454 Figure 38 and 39 who going from a gain of +1 V/V to +2 V/V that the Cload capability increases. So the Cload capability comes down how you plan to apply the op amp in a circuit configuration.

Most any op amp can be set up to drive a larger Cload than is shown in the datasheet graphs by applying compensation techniques. The simplest is a resistor added in series with the op amp output, after the feedback connection. That compensation technique is often referred to as the Riso (isolation resistance) technique. It is simple, but if the op amp has deliver much load current the voltage drop across Riso may be an issue. There are alternate compensation techniques that can be applied where the drop is accounted for, but the compensation circuit is more complex.

If you have some idea about what you need the OPA454 to do in terms of the application requirements, closed-loop gain, inverting or non-inverting configuration, required bandwidth and Cload, we should be able to provide some advice.

Regards, Thomas

PA - Linear Applications Engineering