Magnetic disk drive with effective AGC control of servo signals by selectively varying A/D converter reference level

摘要

A magnetic disk drive provided with a computational control circuit for changing the reference level of the A/D converter so that the outputs of A/D conversion are kept constant at all times, which are obtained from integrated output peak values of the sector servo signals on a track having been read in reading a magnetic disk on which sector servo signals are recorded in advance. For the reference level of the A/D converter, values such that the outputs of the A/D conversion on the innermost and outermost tracks become constant are selected in advance, respectively. Thus, that reference level is obtained on the basis of the above values.