| 摘要 |
PURPOSE:To reduce a read data error rate by controlling a disk revolving speed so that the data window signal is in synchronism with a reference frequency. CONSTITUTION:A read information signal 8 is inputted to a variable frequency oscillator (VFO circuit) 2 through the head output 1. A phase detector 4 compares the phase of a data window signal 9 outputted from the VFO 2 with that of a reference frequency 10 outputted from a reference oscillator 3. Then the signal 9 and the frequency 10 are integrated by an integration circuit 5 to undergo the conversion of voltage and amplified by an amplifier 6. Thus the revolving speed of a DC motor 7 is controlled. The frequency of the signal 8 is changed by said control of the revolving speed and therefore the frequency of the signal 9 is also changed. Thus the control value of the motor 7 is changed. In such a way, the pulse width of the signal 9 can be kept at a fixed level and the read data error factor is reduced.
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