Patent ID: 6147554
Filing Date: 2000-11-14
Classification: G11B

Abstract:
A control signal amplification circuit for amplifying a control signal reproduced by a control head, comprising:a level detection circuit for detecting an output level of an amplification circuit body having an amplification factor determined on the basis of a quantity of feedback fed back from an output terminal of the amplification circuit body to a minus-input terminal of the amplification circuit body to thereby send out a level control signal indicating a result of the detection; anda variable feedback resistance circuit which is connected between the minus-input terminal and the output terminal of the amplification circuit body so that an equivalent resistance value of said variable feedback resistance circuit decreases when the level control signal indicates increase of the output level, and the equivalent resistance value of said variable feedback resistance circuit increases when the level control signal indicates decrease of the output level, said level detection circuit generating the level control signal on the basis of a signal level exceeding a criterion level when the output level of the amplification circuit body in the case where the level of the control signal reproduced by the control head is zero is defined as a reference level and a level different from the reference level by a predetermined level is defined as the criterion level.