PURPOSE: To prevent the polarity of a voltage across an MOS capacitor from being changed against an AC input signal voltage by using the gate-source capacitance of an MOS transistor and charging a bias electric charge synchronously with the switching operation of a switch so as to apply a bias voltage always to the MOS capacitor.

CONSTITUTION: The voltage VB of a bias voltage generating section E is charged to MOS capacitors CM1, CM2 whose gates are connected together through a switch S7 for a prescribed period. An input signal X1 is given to the inverting input of an operational amplifier through a switch S1 and the capacitors CM1, CM2 in series at the next period. Then the voltage acrossing the capacitors is used in a way that the voltage is larger than a threshold voltage VTH. Even when the voltage acrossing the capacitors is changed, the capacitance is unchanged and a stable phase inverting integration device is offered without using any special floating capacitor.