Three op amps Ul, U2, and U3 are connected in the basic instrumentation amplifier configuration. Operating from Â± 5 V, pin 8 of each op amp is connected directly to ground and provides the ac performance desired in this application (high bias mode). PI is for offset error correction and P2 allows adjustment of the input common mode rejection ratio. The high input impedance allows megohms without loading.
The resulting circuit frequency response is 200 kHz at -3 dB and has a slew rate of 4.5 V//xs.