| 摘要 |
PURPOSE:To maintain the linear speed of a disc constant by utilizing a demodulation clock signal used when a data signal is demodulated and comparing in phase the frequency division output of the clock signal with that of a reference signal, thereby generating a motor drive control signal. CONSTITUTION:A data signal detected by a pickup 1 is supplied through an amplifier 3, a waveform shaper 4 to a demodulator 5 and a demodulation clock signal generator 6. The output of the generator 6 is divided in frequency by a frequency divider 11, inputted to a phase comparator 8, which compares the output of a reference oscillator 9 with the output divided in frequency by a frequency divider 10. The output of the comparator 8 is inputted through a low pass filter 13 to a motor drive circuit 14, thereby controlling the rotation speed of the motor 12. The demodulator 5 outputs binary data in response to the length of the data signal on the basis of the clock signal. |
