PURPOSE: To obtain an ideal output and to stabilize an action by executing an integration action with a first switched capacitor, and virtually grounding the inversion input terminal of an inversion amplifying circuit with a second switched capacitor when the prescribed integrated output is obtained.

CONSTITUTION: First and second capacitors 4 and 6 are connected to the input terminal of an inversion amplifying circuit 2, and an input signal is inputted through the first and second switched capacitors 4 and 6 to the input terminal of the inversion amplifier 2. At such a time, the integration action is executed by the first switched capacitor 4, when the prescribed output is obtained during the integration action, the input of the inversion amplifying circuit 2 is virtually grounded by the second switched capacitor 6. and the output is fixed.