PURPOSE: To compensate the change of the temperature of an amplification and to obtain a stable reproduced output by forming the reference voltage of a differential amplifier by a current obtained by connecting respective current mirror circuits constituted of plural NPN and PNP transistors.

CONSTITUTION: The value of a resistance 22 is defined to be R2 and the area of the emitter of the NPN transistor(TR) 21 is defined to be (n) times as large as the NPN TRs 19, 23. When the mirror ratio of the current mirror constituted of the PNP TRs 24, 25 is defined to be '1', this combination forms a band gap reference circuit to have a circuit current of I2=(kT/q).ln(n)/R2 (q is an electron charge, T is an absolute temperature and k is a Boltzmann constant). This current is caused to pass to a resistance 26 connected between a non- inversion input terminal and a source voltage and have the reference voltage. Since a direct current feed back is applied so as to make both the input terminal potentials of an amplifier 14 equal, the current I2 is passed to a resistance 16 in the potential of the non-inversion input terminal of a differential amplifier 13 to change the temperature. The amplification of a cascode amplifier does not include the term of the change of the temperature to obtain an amplified output having no change of the temperature.