Brushless DC motors have permanent magnets on the rotor and externally commutated coils on the stator. The electronic commutation replaces the function of the brushes in a DC motor and typically drives the stator coils in steps based on the sensed rotor position. They differ from a PMSM primarily in that the B-emf waveform induced by rotor spinning has a trapezoidal shape. The primary benefit of a brushless DC motor is it's inherent efficiency and reliability. These motors are becoming more common as designers press for improved efficiency in the system. Typical configurations are a three phase motor driven by 3 half bridges. In low voltage applications the drivers can be integrated into a smart power IC. For higher voltages discrete IGBT or MOSFET and high voltage gate driver ICs are used for the half bridges. Power modules integrating three half bridges and related gate driving stage can also be used. For many applications, sensorless drives have eliminated the need for the speed/position sensors used in the past.