PURPOSE: To obtain an amplified output without distortion in response to an input signal with fidelity, by using a current mirror circuit excellent in the linearity for an output signal lead-out section of a differential amplifier section.

CONSTITUTION: TRs 16, 17 forming a current mirror circuit are connected to one output section of the differential amplifier section comprising differential pair transistors (TRs) 1, 2 and a constant power supply TR3. The output signal leading-out section comprising the TRs 16, 17 and a TR18 is formed. Further, a bias circuit comprising TRs 23∼25 is connected to the base of the TR18. Moreover, the output signal leading-out section including the current mirror circuit and the bias circuit are connected to the differential pair TR2. Each current mirror circuit is operated with an excellent linearity by selecting suitably a constant current value flowed to each bias circuit. Thus, the amplified output without distortion in response to the input signal with fidelity is obtained.