SBOS690A July 2016 – December 2019 OPA2626
The circuit shown in Figure 54 measures the dc input offset related parameters of the OPA2626. Input offset voltage, power-supply rejection ratio, common-mode rejection ratio, and open-loop gain can be measured with this circuit. The basic test procedure requires setting the inputs (the power-supply voltage, VS, and the common-mode voltage, VCM), to the desired values. VO is set to the desired value by adjusting the loop-drive voltage while measuring VO. After all inputs are configured, measure the input offset at the VX measurement point. Calculate the input offset voltage by dividing the measured result by 101. Changing the voltages on the various inputs changes the input offset voltage. The input parameters can be measured according to the relationships illustrated in Equation 1 through Equation 5.