Agere Systems Inc.

Jason A Christianson

Cameron Carroll Rabe

Michael John O'Brien

David W Kelly

Carl F Elliott

Ronen Malka

Boris Briskin

An apparatus and method for controlling the common mode voltage across a data storage device write head. The write current is supplied by a first plurality of parallel current sources each independently activated to limit the common mode voltage generated across the write head. A plurality of parallel resistive elements responsive to current supplied by a second plurality of parallel current sources bias an output transistor that further controls the write current. Each of the plurality of parallel resistive elements and each of the second plurality of parallel current sources is also independently activated to limiting the common mode voltage generated across the write head.

Apparatus and method for controlling common mode voltage of a disk drive write head

An apparatus and method for providing electrostatic discharge protection for a disc drive read head. A pair of depletion mode MOSFETS, and a fuse associated with each are disposed between the read head output terminals. The MOSFETS are controlled to an 'off' state for testing the preamplifier prior to assembly of the read head. After assembly of the head, a second pair of MOSFETS is gated to an 'on' state to open the fuses and thus permit normal operation of the read head.

Method and apparatus for protecting magnetoresistive heads from electrostatic discharge

A magnetic data storage and retrieval system includes a magnetoresistive head, a resistor, a preamplifier circuit, a voltage measurement circuit, and a resistance calculation circuit. The preamplifier circuit is operably coupled to the magnetoresistive head and the resistor, and applies a first current to the magnetoresistive head and a second current to the resistor. The voltage measurement circuit measures a first voltage across the magnetoresistive head and a second voltage across the resistor. The resistance calculation circuit calculates a resistance of the magnetoresistive head based upon the first and second voltages.

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Apple Valley, MN, United States of America

Jason A Christianson