Browse Prior Art Database

Magnetoresistive Head Drive Circuit

IP.com Disclosure Number: IPCOM000085546D
Original Publication Date: 1976-Apr-01
Included in the Prior Art Database: 2005-Mar-02
Document File: 2 page(s) / 42K

Publishing Venue

IBM

Related People

Schwarz, TA: AUTHOR

Abstract

Multiple elements of a magnetoresistive (MR) head are driven by a common balanced capacitorless AC drive having high-input impedance, to prevent loading of the element output signals. The elements are split into two groups A and B. AC switching currents, 180 degrees out-of-phase, are provided to the respective groups.

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Magnetoresistive Head Drive Circuit

Multiple elements of a magnetoresistive (MR) head are driven by a common balanced capacitorless AC drive having high-input impedance, to prevent loading of the element output signals. The elements are split into two groups A and B. AC switching currents, 180 degrees out-of-phase, are provided to the respective groups.

The two AC switching currents switch on odd and even transistors, respectively, of transistor pairs TN1 through TNN. 2I/-/s from transistors TS1- TSN is switched through the heads in opposition to the constantly provided current I/+/s from transistors TP1-TPN.

The shunttsense current Is is determined by the resistor Rs and the positive voltage +V operating on the emitter diode of T1. This causes the collector currents of T2 and TP1-TPN to be approximately Is, thus providing the positive shunt/sense currents I s for each MR element. The emitter diode of T3 is driven by Is from T2 to control the currents Is in transistors TS1-TSN.

The transistors TS1-TSN are paired to draw 2I/-/s through the active transistor in each switching pair Thus, the AC bias current through each element alternates between I/+/s and I/-/s. The MR element outputs are sensed at terminals 1-N.

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