A power circuit includes a power transistor for feeding a load current to a load, a measuring transistor for coupling out a measurement current dependent on the load current, at least two coupling transistors for dividing the measurement current into an internal measurement current and into an external measurement current, wherein the external measurement current can be fed to an external evaluation circuit, and the internal measurement current is fed to an internal evaluation circuit for evaluation. A third coupling transistor can be coupled to the measuring transistor if a measuring device determines a non-coupled state, and the third coupling transistor can be decoupled from the measuring transistor if the measuring device determines a coupled state. The measuring device determines the coupled state if the external evaluation device is coupled to the power circuit, and the measuring device determines a non-coupled state if the external evaluation device is not coupled to the power circuit.