To provide an operating circuit for generating ratio current, which can be composed of only elements with CMOS process, is capable of reducing the number of elements to be used and high integration, and is operable at a low cost and a low voltage.

An operating circuit is composed of the following components: a plurality of signal input terminals T111, T121; a plurality of first bias circuits 111, 121, which set an input terminal connected with each of the signal input terminals to a specified voltage value; a plurality of logarithm compression circuits 112, 122, which perform logarithm compression for input current inputted to each of the signal input terminals, a plurality of reverse logarithm extension circuits 113, 123, which perform reverse logarithm extension for an output signal of each of the logarithm compression circuits; a plurality of output circuits 114, 124, which output an operating signal transmitted to each of the reverse logarithm extension circuits; a second bias circuit 101, which sets an input terminal connected with each of the output circuits to a specified voltage; a first current source I101, which is commonly connected with each of the output circuits; and a plurality of signal output terminals T112, T122 connected with each of the output circuits.