Patent ID: 7830633

Claim:
A head IC, which adjusts an amplitude level of head read signals and outputs the signals to a read channel having an AGC amplifier, comprising: a first differential amplifier, which amplifies the read signals using a preset first gain value; a second differential amplifier, which amplifies output of the first differential amplifier using a preset second gain value; and an AGC circuit, which takes a difference between an output amplitude level of the first differential amplifier and a reference level, automatically adjusts said first gain value of the first differential amplifier by feedback loop control according to prescribed pull-in characteristics, so that a center value in the input amplitude level range of the second differential amplifier is a target, and after completion of automatic adjustment of the first gain value of the first differential amplifier, takes a difference between the output amplitude level of the first differential amplifier and a second reference level, and automatically adjusts the second gain value of the second differential amplifier by feed-forward control according to prescribed pull-in characteristics so that the center value in the input amplitude level range of the read channel is a target.