PURPOSE: To attain the compression of dynamic range of capacitance, reduction in the element sensitivity and unit capacitance value and also the area of capacitor and power consumption by using a switch so as to realize a filter and an equalizer having frequency selectivity.

CONSTITUTION: Switches 18 are all turned on in realizing an LC ladder simulation type switched capacitor filter. In realizing cascade connection of secondary circuits, the switches 28 are all turned off. The switches 18 are mounted on a semiconductor substrate and the switching of them is controlled externally. The capacitance value of the capacitors in the secondary circuits is set by external control. Since an LPF, a BPF and an HPF are realized in a signal flow graph when the switches 18 are turned on, the constitution where the switches 18 are turned on is used when the filters are realized. On the other hand, the equalizer of an optional form is realized by turning off the switches 18, that is, opening a feedback loop, and using the entire circuit as the secondary circuits in cascade connection, when this system is used as the equalizer.