Patent ID: 7564204

Claim:
A motor speed control circuit which controls a rotational speed of a motor by controlling an amount of current flowing through a drive coil of the motor, comprising: a reference voltage circuit that generates a reference voltage corresponding to a speed-specifying signal inputted to specify the rotational speed of the motor; a speed voltage circuit that generates a speed voltage varying in level depending on an actual rotational speed of the motor; a clamp circuit that sets an upper limit level and a lower limit level for the speed voltage generated by the speed voltage circuit, the upper limit level and the lower limit level within an output voltage range of the reference voltage circuit; a comparator that has the reference voltage generated by the reference voltage circuit and the speed voltage limited in level by the clamp circuit applied thereto and compares the two; and a control signal generator that generates and outputs a control signal for controlling the amount of current flowing through the drive coil based on a comparing result of the comparator.