Patent ID: 7567749

Claim:
A motor control circuit, comprising: a pulse width modulation (PWM) signal generating circuit for generating a square wave with a sequence of alternating on-time and off-time; a driving circuit having a plurality of transistors; and a waveform-shaping circuit, connected between the PWM signal generating circuit and the driving circuit, wherein the waveform-shaping circuit has a plurality of waveform-shaping units respectively connected to the transistors for adjusting both the rise-time and the fall-time of the square wave to be within a predetermined range of the square wave period; wherein the driving circuit outputs a driving signal to a fan motor according to the adjusted square wave; wherein the waveform-shaping circuit includes an operational amplifier, and a plurality of resistors and capacitors, one of the resistors being connected to ground, another of the resistors being electrically connected with the operational amplifier in parallel, and the capacitors being electrically connected with the resistor and the operational amplifier in series and in parallel, respectively.