Patent ID: 7224135

Claim:
A motor drive system comprising: a motor having two terminals; a power amplifier circuit coupled to said motor; a pair of current mirrors coupled to said power amplifier circuit; a plurality of selection switches coupled to said current mirrors, and a digital to analog converter coupled to said selection switch devices; wherein said power amplifier circuit is comprising a pair of high side transistors having current paths connected between respective terminals of said motor and a voltage source, and a pair of low side transistors having current paths connected between respective terminals of said motor and the electrical ground terminal; wherein said current mirrors comprise a reference device biased at a first current, responsive to the output of said digital to analog converter, and a differently sized interconnected transistor of said pair of low side transistors of said power amplifier circuit conducting an output current which is a scaled value of said first current; wherein said selection switches operate to select one transistor of said pair of high side transistors of said power amplifier circuit and one of said pair of current mirrors to establish a current path through the selected transistors and the motor in response to a current polarity signal, such that at any time two transistors of said power amplifier circuit are turned on and two transistors of said power amplifier circuit are turned off; wherein the input of said digital to analog converter is a digital signal whose most significant bit is representative of said current polarity signal and the output of said digital to analog converter is said first current, representative of the current to be applied to said motor through the selected current mirror, and whereby said motor drive system receives a digital signal representative of a current and its polarity and imposes a scaled value of said current to said motor.