PURPOSE: To reduce an overall capacity by substituting a part of capacitors by impedance converters and capacitors in switched capacitor filter SCF.

CONSTITUTION: In the SCF consisting of operational amplifier A, capacitors C2 and C3, and analogue switches SW1 and SW2 which are switched periodically by proper clocks, capacitor C2 is substituted by the impedance converter consisting of operational amplifier A, resistances R1 and R2, and capacitor C2'. At this time, since the capacity ratio of capacitors C1 and C2 can be changed to the ratio of resistances R1 and R2 accurately, an SCF where the overall capacity is reduced in comparison with the conventional SCF can be constituted by setting the ratio of resistances R1 and R2 to a prescribed value, so that the chip size for integration can be reduced.