Patent ID: 7675260

Claim:
A motor driving apparatus, comprising: a control unit which detects a rotation frequency of a motor to be driven and generates a control voltage in a manner such that the rotation frequency thereof is brought close to a desired rotation frequency; a drive unit which drives the motor based on the control voltage generated by said control unit; and a start circuit which fixes the control voltage to a predetermined initial voltage at the start of driving the motor; wherein the control unit includes a clamping circuit structured to set an upper limit and a lower limit of the control voltage; and wherein the clamping circuit comprises: a first transistor of NPN type having its base supplied with a minimum clamping voltage corresponding to the lower limit; a second transistor of PNP type having its base supplied with a maximum clamping voltage corresponding to the upper limit; a third switch provided between the emitter of the first transistor and an output terminal of the control unit; and a fourth switch provided between the emitter of the second transistor and the output terminal of the control unit.