Two-wire transmitter

A two-wire transmitter that is connected to an external circuit via two transmission lines and that operates by using an input voltage and a current signal supplied from the external circuit, the two-wire transmitter comprising:

• a constant current circuit that controls the current signal in accordance with a detection result from a sensor;
• and
• a shunt regulator circuit that controls a circuit voltage in accordance with the input voltage,
• wherein the shunt regulator circuit controls the circuit voltage such that the circuit voltage increases as the input voltage increases,
• the constant current circuit includes a transistor connected between one of the transmission lines and the shunt regulator circuit such that a current flowing through the transistor flows from the one of the transmission lines toward the shunt regulator circuit,
• the shunt regulator circuit controls the circuit voltage such that a voltage between terminals of the transistor in the constant current circuit becomes a predetermined voltage and such that the circuit voltage is smaller than the input voltage by the predetermined voltage, and
• the predetermined voltage is a voltage at which the transistor is not saturated.