To reduce offsets in normal operation and to enable a high-speed operation at the time of a transient response while realizing both an output current capability and low current consumption.

A current amplifier comprises: a signal amplifying circuit 10 for amplifying signals corresponding to the difference of input signals IN(+) from reference signals IN(-); a current output circuit 11 for outputting an output current in a prescribed size from the node of an output source transistor and an output sink transistor; and a bias current circuit 20 composed of an output current detection circuit 21 for detecting the output current from the current output circuit 11 and outputting binary signals and a bias current output circuit 22 for switching a bias current and outputting it to the signal amplifying circuit 10 corresponding to the binary signals outputted from the output current detection circuit 21. The binary signals of the output current detection circuit 21 are outputted to a switch 23, and the bias current Ib to be outputted from the bias current output circuit 22 to the signal amplifying circuit 10 is increased.