PURPOSE: To simplify the constitution of a switched capacitor filter itself, and to make unnecessary a clock preventing filter. etc., by forming a part of the switched capacitor filter with an active filter.

CONSTITUTION: An input signal 115 is filtered to an analog basis by an active filter 140. The filtered output signal is integrated by a switched capacitor 120 according to a change-over switch 125 switched at a desired timing. A filtering signal 129 is filtered to the analog basis by an RC active filter 130. Quantizing noise is eliminated from the filtered output.