PURPOSE: To obtain a small-sized tertiary low-pass filter with low power consumption by using switching capacitor circuits as resistance elements of an impedance converting circuit (FDIC circuit) having frequency dependency.

CONSTITUTION: The switching capacitor circuits 13 and 14 are charged and discharged repeatedly by clocks A and B and have positive equivalent resistance values. A switching capacitor circuit 12, on the other hand, is provided with the inverted polarity of an input by the clocks A and B and has a negative equivalent resistance value. Consequently, a circuit constant is selected properly to form a tertiary low-pass filter which has a 3.3kHz cutoff frequency when using, for example, a 1.6pF capacitor C0, 2.13pF C1, 1.066pF C2, 128kHz clocks A and B, 0.324pF capacitor Cg0, 0.147pF Cg1, and 0.384pF Cg2.