PURPOSE: To prevent the generation of signal distortion due to mismatching by correcting mismatching of pair transistors (TR) constituting a circuit (Gilbert circuit) using logarithmic coversion characteristics of TRs.

CONSTITUTION: Output currents Iout1 and Iout2 obtained in the first and the second signal output terminals 22 and 23 are expressed with equations Iout1=IC2+ IC3=(IO+IB)IIN2/(IIN1+IIN2) and Iout2=IC5+IC6=(IO+IA) IIN2/(IIN1+IIN2). In equa tions, IA, IB, and IO are currents flowed to the first constant current source 24, the second constant current source 25, and the third constant current source 26 respectively and IIN1 and IIN2 are input currents. Since a ratio of output current, namely, Iout1/Iout2 is equal to (IO+IB).IIN2/(IO+IA).IIN1 and currents IA, IB, and IO are determined by constant current sources 24∼26 respectively, the current IA of the constant current source is adjusted to keep linearity if signal distortion is generated by mismatching of TRs 12∼14 and TRs 17∼19.