Thermal asperity compensating method, data reproduction error compensating method, automatic gain control system and magnetic disk unit

摘要

A magnetic disk unit lowers a possibility to cause data reproduction errors by setting a gain of a variable gain amplifier (VGA) at a predetermined fixed level for a predetermined time when an output from the VGA which amplifies an input signal is changed to a value smaller than an optimum value upon occurrence of a thermal asperity and then restoring a variable gain condition so that an output amplitude automatically has a certain preset value.