SBOS070D October 1997 – December 2019 OPA548
A unity gain noninverting application could be provided by simply connecting the output of an operational amplifier back to its input, with the signal applied to the noninverting input. Power operational amplifiers are frequently subject to unpredictable load impedances that can cause instability. Increasing gain can enhance stability. Furthermore, the feedback network provides locations for further opportunities for stability enhancing components if necessary.
In this application two 10-kΩ resistors are used for the input and feedback resistance, which would normally result in a noninverting gain of 2. Adding a voltage divider consisting of R1 and R2 reduces the input signal by half before it is applied to the operational amplifier. In this case the solution just happens to restore us back to the desired overall gain of 1. This solution using an identical pair of resistors before the noninverting input between the signal and ground creates what is known as a difference amplifier.