PURPOSE: To improve greatly the through rate and at the same time to omit a complicated bias means by using a capacitor to secure connection between the common current path electrodes of the 1st differential amplifier and the 2nd differential amplifier of the opposite polarity to the 1st amplifier.

CONSTITUTION: The NPN transistors (TR)31 and 32 form a differential pair as the 1st differential amplifier; while PNP TRs 34 and 35 form a differential pair as the 2nd differential amplifier respectively. Constant current sources 33 and 36 have stable drives in a low frequency area where the through rate is not so important, and an amplification output can be obtained. However a current higher than a level decided by a constant current source flows through routes of the TRs 31 and 35 as well as TRs 32 and 34 since a capacitor 37 transmits high frequencies in a high frequency area where the through rate is an important factor. As a result, the through rate is never deteriorated to secure the stable amplification characteristics over a wide range of frequencies.