Current output circuit and two-wire transmitter

A current output circuit for a two-wire transmitter includes a first current source circuit configured to output a first current controlled by a control voltage generated based on a physical quantity, a second current source circuit configured to output a second current controlled by the first current, a first shunt voltage source circuit configured to generate an internal power source of the two-wire transmitter from the second current, a third current source circuit configured to generate a third current controlled by a reference voltage, and a second shunt voltage source circuit configured to generate a power source of the second current source circuit by the third current. The current output circuit is configured to output a predetermined current controlled by the control voltage based on the first current, the second current and the third current to an external circuit through two transmission lines.