PURPOSE: To obtain the sine wave type filter characteristics and thus miniaturize a switched capacitor filter, by providing a switch that performs a control with the 1st phase clock plus a switch that performs a control with the 2nd phase clock to a sampling capacitor.

CONSTITUTION: The analog signal supplied from the input terminal 11 receives a sampling in each fixed period fc, 2fc and 3fc and then charged to the sampling capacitor 13. The electric charge of the capacitor 13 is supplied to the current integral network 16 for actuation of the same network. The switches 17 and 21 that operate with the 1st phase clock 1 plus the switches 18 and 19 that operate with the 2nd phase clock 2 of the opposite phase to the 1st phase clock are provided at the input side of the filter main body 15. These switches are turned on and off to obtain the filter characteristics of the sine wave type curve 25. Thus the folded noise is attenuated at the odd-order frequencies fc and 3fc by the input part itself. In such way, the prefilter attached externally can be simplified with a small size hust by addng two units of switches to a conventional circuit.