PURPOSE: To reduce errors in the temperature variation by connecting a partial voltage resistance and a diode in series to a d.c. power source to ground while the base, collector and emitter of a transistor are connected to the voltage division point of the partial voltage resistance, the power source and the earth through respective resistaces.

CONSTITUTION: A transistor (TR) Q2 connected to resistance (R) 1 and R2 and a diode is connected in series to a variable d.c. power source Vcc, the base of a TRQ1 connected to a connection point a between R1 and R2 though RB, the power source Vcc connected to the collector of the TRQ1 through RC and RE connected to the emitter of TRQ1 to ground. With such an arrangement, variation in the base voltage VBE (T) of TRQ1 is observed with TRQ2 connected to the diode connected to the base side of TRQ1 thereby reducing effect from the temperature in the measurement the amplification factor h'FE of TRQ1.