To eliminate the influence caused by the configuration for adjusting the cut-off frequency of an LPFF circuit 21 of a variable-frequency filter circuit wherein by providing in it two LPFs F1, F2 comprising gm amplifies, a microcontroller 24 so controls the current-value converting circuits B1, B2 of the two LPFs F1, F2 and so changes the reference currents IB1, IB2 of the two LPFs F1, F2 as to change its cut-off frequency.

By providing an adjusting mode in a variable-frequency filter circuit, the discrepancies of its LPFs, F1, F2 for filtering output signals are so sensed as to compensate the discrepancies. Thereby, the influence caused by the relative variations of circuit elements with respect to the circuit layout of the variable- frequency filter circuit is more suppressed, and its consumption current is more reduced and the diffractions of interference signals to its received signal are more prevented, in comparison with the configuration wherein the discrepancies are sensed and compensated by providing separately a reference filter, etc. In the case of the present variable- frequency filter circuit, there can be so determined previously and accurately by simulations the discrepancies caused by such dynamic changes as the changes of its power supply voltage and its ambient temperature which can not be sensed in real time as to store these discrepancies in a data memory 39.