PURPOSE: To obtain an impedance switching circuit which can be converted easily into an IC by having a combination between two amplifiers containing the 1-fold gain and two switching elements interlocking two linear or nonlinear impedance elements having equal characteristics to each other.

CONSTITUTION: In a circuit B, a circuit in which an impedance element 11 and the collector of a bipolar transistor (TR)Q6 are connected in series from the input side and has an emitter connected with the output terminal of an amplifier 12 of gain 1 is connected in parallel to a circuit in which the input terminal and the output terminal of an amplifier 13, the collector and the emitter of a TRQ7 and an impedance element 14 are connected in series from the input side. The elements 9 and 14 have equal characteristics to each other, and only external capacitors C5 and C6 are provided at the outside 4 of an IC. While a resistance, etc. are provided at the inside 5 of the IC. In such a constitution, TRs Q4∼Q7 interlock with each other and turned on and off. Thus the impedance value is switched between an input terminal 2 and an output terminal 3 to have a high-speed or a low-speed operation in response to the circuit time constant. As a result, a switching circuit can be converted easily into an IC.