Circuit for varying a loop gain of a spindle servo

摘要

In a spindle servo circuit for controlling rotation of a disc, a loop gain of a spindle servo can be varied and a reproduced synchronizing signal from the disc and a reference signal are compared with each other. A phase difference signal and a frequency difference signal that are compared results are chopped by a chopper clock. A loop gain of a servo circuit is varied by varying a duty ratio of the chopper clock and the loop gain can be varied by controlling the duty ratio of the chopper clock in response to a radius of the disc or a revolution rate of the disc.