Potential sensor for detecting voltage of inspection target at non-contact condition to attain higher speed of inspection

摘要

A potential sensor, includes a field effect transistor, a power supply and a switching device. The power supply supplies a direct current voltage to a gate electrode of the field effect transistor. The switching device switches between connecting the gate electrode to the power supply and disconnecting the gate electrode from the power supply. When the gate electrode is connected to the power supply, the field effect transistor is in action. When the gate electrode is disconnected from the power supply, the field effect transistor is in action.