Because of powerline interference, the ECG signal contains many common-mode components. Sometimes, these common-mode components can affect the waveform seriously. To meet the requirements of improving the overall common mode rejection ratio of the system, the driving electrode is usually the output electrode, which output the common-mode component of the ECG signal collected by the ECG front end to the human body in the reverse direction. Generally, the driving electrode can be placed anywhere on the human body, but it is better to put it on the right leg, which is also called "right leg drive", because the distance from the right leg to other input electrodes is approximately equal.