PURPOSE: To facilitate easy conversion into an IC by having a combination between two amplifiers which have high input and low output impedances having the 1-fold gain when the switch signal is on and then a high output impedance having zero gain when the switch signal is off respectively and two impedance elements which have equal characteristics to those of said two amplifiers.

CONSTITUTION: In a circuit B, a circuit in which an impedance element 11 and the output terminal of an amplifier 12 are connected successively from the input side is connected in series to a circuit in which the input and output terminals of an amplifier 13 and an impedance element 14 are connected in series from the input side. The elements 11 and 14 have equal linear or nonlinear characteristics, and amplifiers 12 and 13 and transistors TRs Q3 and Q4 are turned on and off by the switch signal of a terminal 1. The amplifiers 12 and 13 have equal characteristics to each other and have the high input and low output impedances with the 1-fold gain when the switch signal is on and then a high output impedance with zero gain when the switch signal is off respectively. Only external capacitors C5 and C6 are provided at the outside 4 of an IC. Thus the impedance is switched between an input terminal 2 and an output terminal 3. In such a way, an impedance switching circuit can be converted easily into an IC.