A voltage of a first capacitor is compared with a threshold voltage and a signal corresponding to the comparison result is generated at each of a first timing during a period after the transfer of a positive charge has ended and before the transfer of a negative charge starts and a second timing during a period after the transfer of the negative charge has ended and before the transfer of the positive charge starts. In each of the case where a positive charge is transferred and the case where a negative charge is transferred, operations (digitization of an integrated value and a feedback operation) of a delta sigma modulator are performed.