PURPOSE: To prevent fluctuation in an output signal due to an effect caused with other circuit in common grounding connection by connecting an amplifier means to a post stage of a main amplifier and feeding back each output of the main amplifier and the amplifier means to an inverting input pin of the main amplifier.

CONSTITUTION: A current amplifier 21 having a prescribed amplification factor is provided between an output pin of a main amplifier 1 and an output terminal OUT. An output signal outputted from the current amplifier 21 is fed back to an inverting input pin (-) of the main amplifier 1 via a resistor R1 and an output signal outputted from the main amplifier 1 is fed back to an inverting input pin (-) via a resistor R2, thereby acting the main amplifier 1 like a differential amplifier. Thus, a voltage Vout of the output signal outputted from the current amplifier 21 is kept constant even when a resistance RL of a load 5 is changed. Thus, a fluctuation of a load connecting to an output terminal or a fluctuation of an output signal due to an effect caused with other circuit in common ground connection is prevented.