PURPOSE: To obtain the current boost circuit with simple circuit configuration by simplifying a bias circuit.

CONSTITUTION: An output of an operational amplifier 11 is given respectively to a resistor 12, and bases of an NPN transistor(TR) 13 and a PNP TR14 and an output of the resistor 12 and emitters of the TRs 13, 14 are connected to a load via an output terminal S. When an input current from the operational amplifier 11 is sufficiently high and the TR 13 or 14 is conductive by a voltage drop across the resistor 12, a current resulting from superimposing a current amplified by the TR 13 or 14 and a current outputted directly from the operational amplifier 11 via the resistor 12 is fed to a load. When the TRs 13, 14 are not conductive by a voltage drop across the resistor 12, a current outputted directly from the operational amplifier 11 via the resistor 12 is fed to the load.