Circuit for varying a loop gain of a spindle servo.

摘要

In a spindle servo circuit for controlling rotation of a disc (1), a loop gain of a spindle servo (3) can be varied and a reproduced synchronizing signal from the disc (1) and a reference signal are compared with each other. A phase difference signal and a frequency difference signal are compared with a reference signal and the results are chopped by a chopper clock (20). A loop gain of a servo circuit (18) is varied by varying a duty ratio of the chopper clock (20) and the loop gain can be varied by controlling the duty ratio of the chopper clock (20) in response to a radius of the disc (1) or a revolution rate of the disc (1)