Patent ID: 7821734

Claim:
A head IC for adjusting an amplitude level of a read signal from a head which reads a signal from a recording medium, and outputting the adjusted read signal to a read channel which has an AGC amplifier, comprising: a differential amplifier for amplifying said read signal with a gain being set; an envelope circuit for detecting an output amplitude level of said differential amplifier; a gain error computing unit for computing a difference between said detected output amplitude level and a reference level; a feedback circuit which has a pull-in characteristic that is slower than a pull-in characteristic of the AGC amplifier of said read channel, and for automatically controlling a gain of said differential amplifier according to a gain error amount which is said difference; a peak hold circuit for holding a maximum value of said output amplitude level; and an amplitude limiting circuit for cutting an input of said output amplitude level which is smaller than said holding value of said peak hold circuit to said gain error computing unit according to said holding value, when said gain is initialized.