The zero potentiometer has no effect on the differential gain of the differential amplifier circuit, but only on the common mode gain. The differential amplifier circuit has the ability to amplify differential mode signals and suppress common mode signals. Differential amplifier circuit, because the circuit structure of the input stage can not be completely symmetrical, the output is not zero when the input is zero-that is, there is so-called offset. Zero adjustment means taking some measures to introduce compensation, so that the output of the circuit is zero when the input is zero.