Operational Amplifier Stability

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Operational Amplifier Stability [Copy link]

By : Tim Green , Linear Applications Engineering Manager, Burr-Brown Product Line, Texas Instruments

An interesting thing happened while writing the “ Six Ways to Keep Capacitive Loads Stable ” section. We selected a CMOS op amp with a “rail-to-rail” output and measured R _OUT , but there was no loop gain in the high frequency region, so we could not determine R _O . Based on the R _O measurement, we predicted the location of the second pole in the amplifier’s “ corrected Aol plot” with a 1μF capacitive load . To our great surprise, the Tina SPICE simulation was off when the “ corrected Aol ” plot was processed by x5 ! Based on the previous first-round analysis results, this error was well beyond the acceptable limit, so we took a closer look at the amplifier output impedance.

uestcfrank

thanks.