PURPOSE: To realize the improvement of an output characteristic with simple constitution by preventing the switching control of other switch elements when a switch element connected to the virtual ground input of an operational amplifier circuit is in an ON state.

CONSTITUTION: When input signal charges are fetched into input side capacitors C1∼Cn, the switch elements Q1∼Qn connected to the capacitors are turned on or off according to the input digital signal values of bits corresponding to respective capacitors. Thus, respective capacitors are discharged according to the input digital signal values, and charged up by a reference voltage VR. When the signal charges of the capacitors C1∼Cn are transmitted to an output side capacitor CO provided between the virtual ground input terminal and an output terminal Vout in the operational amplifier circuit OP, the control of the switch elements Q1∼Q6 connected to the capacitors C1∼Cn is stopped and only switch elements 7 and 8 are turned on.