a sampling capacitor;

a first switch connected between a signal input terminal and one terminal of the sampling capacitor;

a differential amplifier including an inverting input terminal connected to another terminal of the sampling capacitor and an output terminal connected to a signal output terminal;

a reference power supply configured to apply a predetermined voltage to a non-inverting input terminal of the differential amplifier;

a second switch connected between the inverting input terminal of the differential amplifier and the signal output terminal;

a third switch connected between a common connection point of the first switch and the sampling capacitor and the signal output terminal; and

a controller configured to execute on and off control of the first to third switches, wherein

the second switch includes a series circuit of first and second metal oxide semiconductor (MOS) transistors and a potential holding capacitor connected between a node that is a common connection point of the first and second MOS transistors and a ground, and a back gate of the first MOS transistor is connected only to the node together with a source of the first MOS transistor.