Abstract: A differential output circuit for generating a bipolar DC current for an armature winding without requiring a bipolar power source. A combination of transistors and resistors are utilized to effectively apply a bipolar driving current. The use of only transistors and resistors in the differential output circuit enables its easy implementation as an integrated circuit.

Abstract: A drive system for a brushless dc motor to control the magnitude of the torque of a motor which has permanent magnet rotor and Hall generators. Multipliers determine the magnitude of current to each phase armature winding so as to determine the current sharing rate among the armature windings according to the rotation angle of the rotor, whereby degrading of torque uniformity due to variation of Hall generator characteristics is avoided. Each multiplier multiplies 2 signals, one being the output of the Hall generator, the other being the difference between the torque control input and the fed back signal of total armature current. Also a torque direction input is supplied to each multiplier to determine the direction of the rotational torque.