4.3 Capacitive Loads and Stability

One of the key parameters to keep in mind when using the operational amplifier is the load on the output. For heavy resistive loads, the Output Swing may reduce, but the amplifier will remain stable. However, heavy capacitive loads introduce a phase shift of the output in relation to the input (note that there may be a slight phase shift even in resistive operating conditions). If this phase shift causes the output to be too far out-of-phase, then the operational amplifier will begin to oscillate.

The simplest way to stabilize the phase shift is to put a resistor between the output and the capacitive load, as shown below. The exact value of the resistor will vary depending on the load capacitance and the specific characteristics of the operational amplifier, such as maximum output current and slew rate.