A control unit for driving a regulating transistor (2) of a fan arrangement, in which the regulating transistor (2) is connected in series with an electronically commutated fan (1), having control means (5, 6, R1, R2) for the analog driving of the regulating transistor (2) with a control signal (U.sub.control) in a manner dependent on a control input voltage (U.sub.in). The control unit comprises compensation means (R3, R4) for influencing the control signal (U.sub.control) in a manner dependent on an AC voltage component (U.sub.AC) of an operating voltage (U.sub.B) of the fan arrangement, so that the AC voltage component (U.sub.AC) of the operating voltage (U.sub.B) is completely or partially compensated for in a voltage across the fan (1).