The invention relates to a circuit arrangement and a method for operating an electric motor in a direct voltage source, in particular for operating a permanent-magnet-excited DC motor in the direct voltage network of a motor vehicle, having a rotary position transducer (32) for detecting the rotary position of the rotor (20), and having an electronic commutation controller (32) for switching over the current in the armature winding of the stator (12) as a function of the position of the rotor (20). It is proposed that the rotary position transducer (32) is positioned relative to the stator (12) for an early commutation, and that the actual commutation time can be set by means of a delay correction, ascertained by measurement separately for each motor (10), in the electronic commutation controller (30).