Clock extracting device of a disc reproducing apparatus having a gain command unit for designating a loop gain

Abstract

A clock extracting device of a disc reproducing apparatus includes an information read-out member for reading information signals from a disklike information recording medium; a voltage control oscillator; a phase comparator; a frequency comparator; a speed sensor for detecting the frequency of the output of the voltage control oscillator at a reference clock so as to output a speed signal; a gain command unit for designating a loop gain of a clock extracting circuit in accordance with the speed signal outputted from the speed sensor; a charge pump which discharges or draws electric current in accordance with outputs of the phase comparator and the frequency comparator and changes over an output current value in accordance with a gain command of the gain command unit; and a series circuit of a resistor and a capacitor, wherein the gain command unit issues the gain command such that the loop gain of the clock extracting circuit secures a desired operating point in accordance with a read rate of the information signals.