PURPOSE: To reduce the circuit capacitance ratio wihtout changing the frequency characteristic and to reduce the circuit scale and the manufacture dispersion by forming the filter device with plural input capacitors, feedback capacitors, a switch closed by a clock of phase A, a switch closed by a clock of phase B, and an operational amplifier.

CONSTITUTION: The circuit filter consists of input capacitors 3-8, a feedback capacitor 9, switches 10, 13, 15, 17, 20, 22 closed by a clock of phase A, switches 11, 12, 14, 16, 18, 19, 21, 23 closed by a clock of phase B and an operational amplifier 24, and receives a signal input 1 and outputs a signal output 2. Through the constitution above, when the switches 11, 12, 14, 16 are closed, only the capacitor 5 is used to transfer the charge to the feedback capacitor 9 of the operational amplifier 24 and when the switches 10, 13, 15 are closed, the charge is transferred by the capacitor 5 only. Similarly, when the switches 18, 19, 23 are closed, only the capacitor 8 among the capacitors 6-8 is used for charge transfer and when the switches 17, 20, 22 are closed, only the capacitor 8 is used for charge transfer.