PURPOSE: To eliminate the need for mounting a high precision resistor deciding a cut-off frequency to the outside of a semiconductor integrated circuit and to make the circuit small by selecting number of connected filter constant correction circuits each connecting to a filter constant circuit so as to vary the cut-off frequency.

CONSTITUTION: Plural input signal selection circuits 101-10n receive a same input signal from terminals 111-11n and only one circuit selected by a selection signal from terminals 121-12n extracts the input signal and outputs it externally. Plural amplifiers 131-13n amplify a signal extracted by the input signal selection circuits 101-10n. A filter constant circuit 161 connects to a 1st stage amplifier 131 among the plural amplifiers and a capacitor and a resistor decide the cut-off frequency. Filter constant correction circuits 162-16n. are connected respectively to amplifiers 132-13n after the 1st stage amplifier and connected sequentially in series with the resistor of the filter constant circuit 161 to vary the resistance deciding the cut-off frequency. The single amplifier receiving a signal extracted by any input signal selection circuit is activated to obtain a desired cut-off frequency.