Provided is a receiving circuit that operates in a power supply system different from a transmitting circuit outputting a transmission signal and receives the transmission signal through an AC coupling device where a primary coil through which the transmission signal flows and a secondary coil having a center tap to which a specified voltage is supplied from an external terminal are magnetically coupled, which includes a pulse width amplifier circuit that holds pulse signals appearing at both ends of the secondary coil for a specified period of time and outputs them as hold signals, respectively, and a differential amplifier that compares a voltage of the hold signal and a voltage of the hold signal and outputs a comparison result.