Abstract: In a D.C. brushless motor, a drive coil (11), a drive circuit (40), and an magnetoelectric transducer (19) are mounted on an insulating base plate (7) which is received in a generally cup-shaped yoke (12). The drive coil, drive circuit and transducer are all mounted on a first side of the base plate (7) while terminals (7b) of the drive circuit protrude from the first side. As a result, the base plate (7) is placed on a bottom of the yoke (12) which bottom substantially faces an entire area of a rotor (5) of the motor thereby reluctance of a magnetic circuit formed by said yoke (12) is substantially constant during one revolution of the rotor (5). The base plate may (7) be directly in contact with the yoke (12) so as to facilitate heat dissipation, while the drive circuit (40) and the transducer (19) are hermetically sealed by a synthetic resin (7d).