What is the frequency response of the circuit in E7-3 if a capacitor is added across the feedback resistor?
Why In the inverting op-amp of figure E7-3 the gain is set by the ratio of the feedback impedance to the input resistor, gain = -Zf/R1. Putting a capacitor in parallel with the feedback resistor makes Zf drop as frequency rises, because the capacitor's reactance Xc = 1/(2*pi*f*C) shunts the resistor. So low frequencies see the full resistor and full gain, while high frequencies see a shrinking impedance and falling gain, which is low-pass behavior with a corner at f = 1/(2*pi*Rf*C).
Watch out High-pass is what you get by putting the capacitor in series with the input resistor instead, where the series reactance blocks the low frequencies from reaching the summing junction.
Cap across the feedback resistor shorts out the high-frequency gain: feedback C = low-pass; series input C = high-pass.