Common-mode rejection (CMR) of the INA117 is dependent on the input resistor network, which is laser-trimmed for accurate ratio matching. To maintain high CMR, having low source impedances is important for driving the two inputs. A 75Ω resistance in series with pin 2 or 3 decreases CMR from 86dB to 72dB.

Resistance in series with the reference pins also degrades CMR. A 4Ω resistance in series with pin 1 or 5 decreases CMRR from 86dB to 72dB.

Most applications do not require trimming. Figure 7-2 and Figure 7-3 show optional circuits that can be used for trimming offset voltage and common-mode rejection.