The OPA928 features a patented output stage capable of driving large capacitive loads. Increasing the gain enhances the ability of the amplifier to drive greater capacitive loads. The particular op-amp circuit configuration, layout, gain, and output loading are some of the factors to consider when establishing whether an amplifier can be stable in operation.

For additional drive capability, insert a small isolation resistor (R_ISO) in series with the output; Figure 6-1 shows this resistor. This resistor significantly reduces ringing while maintaining dc performance for purely capacitive loads. However, if there is a resistive load in parallel with the capacitive load, a voltage divider is created, introducing a gain error at the output and slightly reducing the output swing. The error introduced is proportional to the ratio R_ISO / R_L, and is generally negligible at low output levels. R_ISO modifies the open-loop gain of the system for increased phase margin.

Figure 6-1 Extending Capacitive Load Drive With the OPA928