PURPOSE: To make a response at high speed with high accuracy by comparing the first- and second analog voltage while opening-closing the first-, second-, and plural analog switches, and outputting a compared voltage.

CONSTITUTION: When analog voltages V1 and V2 are respectively inputted from input terminals 1 and 2 and a control voltage Vc at an L level is applied to a control voltage input terminal 4, all analog switches 3, 12 and 13 are turned to an conductive state and an analog switch 6 is turned to a non-conductive state. Therefore, both voltages at one end T2 of a capacitor 7 and an output end T3 of an inverter 8 become the 1/2 of a power supply voltage VDD. Next, when the control voltage Vc at an H level is impressed to a control voltage input terminal 4, an operation reverse to the above mentioned operation is executed. Thus, the potential of a connecting point T4 comes to the 1/2 of the potential VDD when short-circuiting the input/output of the inverter, and spike noise can be prevented from being generated when opening/closing the analog switch 12.