8.3.4 Capacitive Load and Stability

The dynamic characteristics of the OPAx180-Q1 are optimized for a range of common operating conditions. The combination of low closed-loop gain and high capacitive loads decreases the phase margin of the amplifier and can lead to gain peaking or oscillations. As a result, heavier capacitive loads must be isolated from the output. The simplest way to achieve this isolation is to add a small resistor (for example, R_OUT equal to 50 Ω) in series with the output. Figure 27 and Figure 28 illustrate graphs of small-signal overshoot versus capacitive load for several values of R_OUT. See the Feedback Plots Define Op Amp AC Performance, application report, available for download from the TI website, for details of analysis techniques and application circuits.

RL = 10 kΩ

100-mV output step

Figure 27. Small-Signal Overshoot Versus Capacitive Load

RL = 10 kΩ

100-mV output step

Figure 28. Small-Signal Overshoot Versus Capacitive Load