8.1: Theory Overview

The upper break frequency, \(f_2\), of a typical amplifier is a function of the circuit gain and the op amp’s unity-gain frequency, \(f_{unity}\). Typical op amps exhibit a 20 dB per decade roll off slope in their open-loop response. When negative feedback is applied, this results in a direct tradeoff between closed-loop gain and \(f_2\). Any increase in gain results in an equivalent decrease in \(f_2\), and vice versa. In other words, the product of closed-loop gain and \(f_2\) must be a constant. This constant can be found on a device data sheet as either \(f_{unity}\) or GBW (short for Gain-BandWidth product).

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