7.3.5 Stability With High Capacitive Loads

Operational amplifiers have reduced phase margin when there is a direct capacitance on the output. The stability is affected most when the amplifier is set to unity gain. Small signal response to a step input of 100 mV reveals the loop stability with a range of capacitors. See SLVA381 to correlate response waveform to phase margin. The responses at 1 nF or less indicate acceptable phase margin. The responses at 1 uF and above indicate good phase margin.

Figure 7. Small-Signal Response