The dynamic characteristics of the OPAx140 have been optimized for commonly encountered gains, loads, and 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 (R_OUT equal to 50 Ω, for example) in series with the output.

Figure 6-19 and Figure 6-20 illustrate graphs of Small-Signal Overshoot vs Capacitive Load for several values of R_OUT. Also, see the Feedback Plots Define Op Amp AC Performance Application Bulletin, available for download from www.ti.com, for details of analysis techniques and application circuits.