A discharge circuit holds the potential difference between a power supply terminal and reference potential terminal at a predetermined value. The gates of a first pMOSFET and first nMOSFET are connected to an input terminal. A second pMOSFET is connected between the first pMOSFET and power supply terminal, and has a gate to which a first signal is supplied. A second nMOSFET is connected between the first nMOSFET and reference potential terminal, and has a gate to which a second signal is supplied. A detection circuit outputs the first signal which turns on the second pMOSFET and the second signal which turns on the second nMOSFET, while the potential difference is held at the predetermined value. The detection circuit outputs the first signal which turns off the second pMOSFET and the second signal which turns off the second nMOSFET, while the potential difference deviates from the predetermined value.