Method for controlling read head bias current, and magnetic disk data storage device

PURPOSE: To compensate the deterioration of performance due to the variability of a component in a magneto-resistive head by setting a high value which does not exceed the specified rate of the optimum value of bias current. CONSTITUTION: In the partial block diagram of a disk driving device incorporating a general-purpose error measuring GEM circuit, a GEM circuit 33 is shown. Control is executed by a micro processor 30 and a head/disk assembly controller 31 in the disk driving device and the controller 31 receives input from the error measurement circuit of the GEM circuit 33. Bias current is set by a three bit signal sent to a pre-amplifier circuit 17 in an arm electronic circuit in response to an error value processed by the GEM circuit 33. The maximum value of bias current Ib is used only in a data restoration procedure when instantaneous high current does not damage the life of the MR head. For restoration, the high value which does not exceed the specified % increase of the optimum value is used. COPYRIGHT: (C)1995,JPO