PURPOSE: To realize downsizing by eliminating a constant voltage supply dedicated for position detecting circuit while obtaining a position detection signal equivalent to conventional one.

CONSTITUTION: The drive circuit comprises a DC motor 53 having a permanent magnet rotor and an armature winding, a circuit 1 for detecting the position of rotor based on the terminal voltage of armature winding, an inverter circuit 51 comprising a plurality of transistors Tr1-Tr6 constituting upper and lower arms, and control means 56 for turning the transistors ON/OFF based on a position detection signal fed through a photocoupler 55. Photodrivers 4d-4f in the control means 56 for feeding power to the bases B of the transistors Tr4-Tr6 constituting the lower arm are connected in parallel between a constant voltage supply 12 and a ground point G2. The position detecting circuit 1 is connected between the constant voltage supply 12 and the ground point G2 and fed with power.