In a current-source circuit in which a first and a second MOS field-effect transistor form a current mirror circuit, wherein a reference current can be supplied to the first MOS field-effect transistor via a third MOS field-effect transistor connected in cascode and the drain electrode of a fourth MOS field-effect transistor connected to the second MOS field-effect transistor in cascode forms an output, the source electrodes of the third and of the fourth MOS field-effect transistors are connected to inputs of an automatic gain control amplifier whose output is connected to the gate electrode of the fourth MOS field-effect transistor. The fourth MOS field-effect transistor is an extended-drain MOS field-effect transistor. The drain electrode and the gate electrode of the fourth MOS field-effect transistor are connected to one another via a further MOS field-effect transistor whose gate electrode is acted on by an operating voltage for the circuit.