In a motor actuator, e.g., a valve actuator, comprising a reversible electrical motor, a drive circuit is providing a stop function, when the torque of the motor exceeds a predetermined maximum torque. The drive circuit is constructed as a two-terminal circuit connected in series with the reversible electrical motor, and the electrical power is supplied to the series connection with a mainly fixed voltage VCC and a polarity which provides the desired rotational direction of the motor. This provides the possibility of having the drive circuit positioned close to the motor and maintaining full torque control and stop function with two wire connections.