Providing electronic commutation and speed control for three-phase brushless dc motors, the 4-Q-EC four-quadrant controller maintains speed control whether accelerating or braking in CW or CCW directions. Commutation and velocity feedback is achieved using Hall-effect sensors and an encoder, respectively. Speed and direction is determined via an external signal voltage of ±10V or via a potentiometer. Additional inputs set current limits or disable power using TTL, CMOS or a switch signal. The output power stage uses MOSFET technology. Supply voltage is 12V to 50V, with a 4V drop at the motor. Maximum continuous current is 6A using an added heat sink. Controller dimensions are 103 x 70 x 39 mm including connector. The connector is removable so the controller can be directly mounted to PCBs. This unit is CE Marked for the European market.