PURPOSE: To eliminate the influence of temperature characteristics of a load and transistors TRs by controlling the current source of a common emitter of a current changeover switch circuit to eliminate the influence of the base current of each TR when the influence of the temperature characteristic of the load is compensated.

CONSTITUTION: A TR Q10 constituting the current source of the common emitter of switching TRs Q3 and Q4 is so operated that the voltage drop due to a resistance R9 is constant. Since a current resulting from addition of not only currents conducted to loads R1 and R2 but also the base current of the TR Q3 or Q4 and that of the TR Q10 is the emitter current of the TR Q10, the base current is supplied to TRs Q9, Q11, and Q12 constituting a current mirror circuit to prevent said two base current components from being conducted to a resistance R9. Thus, the current source is controlled by the current approximately equal to the current conducted to the load R1 or R2.