Most Op-Amps used in closed loop form have an inductive looking output, meaning the output impedance rises with frequency. This can cause all sorts of problems with active filters when the reactive looking output impedance becomes significant relative to the next stage effective input impedance. This also degrades the low pass SK stop band rejection because the series C feeds directly to the Op-Amp output, and why we often used an heavily biased emitter follower (inside the closed loop) at the Op-Amp output, or just forced the Op-Amp output device into Class A operation away from Class A/B, by using a resistor to the negative supply to sink a few millamps.
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