Read circuit in magnetic disk drive

Claim 1

A data reading method in a magnetic disk drive for recording and reproducing data using a magnetic head, comprising the steps of: positioning said magnetic head using a sector servo method; generating a signal based on contents of a sector which corresponds to a position of said magnetic head as read by said magnetic head, said sector including at least one absolute address area containing cylinder data required for a seeking operation of said magnetic head, at least one AGC address area containing a holding gain used in said absolute address areas, a burst servo area containing position data for correcting positional shifts of said head after said seeking operation is recorded, an AGC burst area for determining a holding gain used in said burst servo area, and a data area in which data sent from a host computer is recorded; amplifying said signal generated from said magnetic head by an automatic gain control amplifier (AGC amplifier); setting a tracking speed of said AGC amplifier to a first tracking speed in said AGC address area and in said AGC burst area in accordance with a content of said signal; setting a tracking speed of said AGC amplifier to a second tracking speed in said data area in accordance with a content of said signal; and holding a gain of said AGC amplifier in said absolute address area and in said burst servo area in accordance with a content of said signal.