| 摘要 |
PURPOSE:To accurately detect the speed of a motor by connecting a noise eliminating circuit to a speed detecting coil and a noise-eliminating signal forming circuit. CONSTITUTION:In a CPU 11 data on speed information which is decided in advance so that a head 3 is shifted from one track to another as quickly as possible is generated and output to a differential amplifier 13 via a D/A converter 12. A voltage V1 corresponding to a difference between a voltage of desired speed given from the converter 12 and a voltage of detected speed based on the voltage of a speed detecting coil 31 is output by the amplifier 13 to a drive circuit 15 and a noise-eliminating signal forming circuit 16. The circuit 16 generates a noise-eliminating signal Vnb and outputs it to a noise- eliminating differential amplifier 14. At the amplifier 14 the signal Vnb is subtracted from a speed detection signal Vs based on the coil 13 and a speed detection signal which does not include noise components is output to the amplifier 13. |
