A current source includes a first switching element configured to adjust an output current according to a control signal received at a control input. The current source also includes a reference resistance, which is electrically coupled to the first switching element such that the output current flows through the reference resistance. The latter includes first and second individual reference resistors, connected in series, and a diode connected in parallel to the first reference resistor. The first reference resistor has a higher impedance than the second reference resistor. A controller receives a predetermined reference potential and an actuating signal that constitutes the control signal of the first switching element. A second switching element supplies the controller with an actual value consisting of the voltage across the first and second individual reference resistors, when the element adopts a first switching position and consisting of the voltage drop across the second individual reference resistor, when the element adopts a second switching position.