PURPOSE: To form the generator into one chip IC together with the control and driving circuit of a motor so as to miniaturize it and simplify the constitution by generating the index signal of the motor, making use of the signal of position detection required for the changeover of current application to the motor.

CONSTITUTION: A rotor magnet 1 is made of a permanent magnet magnetized in multiple poles, and it is so arranged that the position of this rotor magnet 1 is detected with position detectors 2, 3, and 4. The outputs of these position detectors 2, 3, and 4 pass amplifiers 5, 6, and 7, and waveform formers 8, 9, and 10, and are input into a synthesizer 11. The synthesized signal 16 of the synthesizer 11 is input into a frequency divider 17, and it outputs an index signal 18. The outputs of the waveform formers 8, 9, and 10 are input into a current application changeover circuit 23, and this output is connected to a driving transistor 27, which performs the current application to driving coils 24, 25, and 26.