PURPOSE: To apply linear conversion or nonlinear conversion, to apply the titled circuit to function conversion and to improve the degree of freedom of a conversion coefficient by providing plural coupling circuits each comprising 2-stage of NPN transistors (TR), a differential amplifier and a current mirror circuit.

CONSTITUTION: The coupling circuit Fa consists of 2-stage of TRs Qa1, Qa2, and the coupling circuit Fb consists, similarly or 2-stage of TRs Qb1, Qb2. Further, bases of the TRs Qa2, Qb2 are connected to a bias power supply VB1 and a common emitter of TRs Qy, Qx constituting the differential amplifier is connected to a current supply terminal P0. Further, the collector of the TR Qx is connected to the collector and base of a TR Q11 constituting the current mirror M1 and the base of a TR Q12. Then currents IPy, IPx are decided by currents Ia1, Ia2 and Ib1. Thus, linear conversion or nonlinear conversion is applied, the titled circuit is applicable to the function conversion such as multiplication/division/power and the decrease in the degree of freedom of conversion coefficient is attained.