Jason William Christianson

US Patent:

7502207, Mar 10, 2009

Filed:

Apr 5, 2005

Appl. No.:

11/099214

Inventors:

Jason A. Christianson - Apple Valley MN, US
Michael John O'Brien - St. Paul MN, US
Cameron Carroll Rabe - Inver Grove Heights MN, US
Carl F. Elliott - Eden Prairie MN, US

Assignee:

Agere Systems Inc. - Allentown PA

International Classification:

G11B 5/127
G11B 5/55

US Classification:

360323, 360110

Abstract:

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.

US Patent:

7701654, Apr 20, 2010

Filed:

Sep 14, 2006

Appl. No.:

11/521568

Inventors:

Jason A. Christianson - Apple Valley MN, US
David W. Kelly - Eagan MN, US
Michael John O'Brien - St. Paul MN, US
Cameron Carroll Rabe - Inver Grove Heights MN, US

Assignee:

Agere Systems Inc. - Allentown PA

International Classification:

G11B 5/09

US Classification:

360 46, 360 66, 360 67, 360 68

Abstract:

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.

US Patent:

20030058566, Mar 27, 2003

Filed:

Sep 26, 2001

Appl. No.:

09/964083

Inventors:

Boris Briskin - Vadnais Heights MN, US
Jason Christianson - Apple Valley MN, US
Ronen Malka - Eden Prairie MN, US

Assignee:

Agere Systems Guardian Corp. - Orlando FL

International Classification:

G11B005/02

US Classification:

360/067000

Abstract:

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.