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AC Bias of Magnetoresistive Head

IP.com Disclosure Number: IPCOM000086190D
Original Publication Date: 1976-Aug-01
Included in the Prior Art Database: 2005-Mar-03
Document File: 2 page(s) / 32K

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Related People

Lewkowicz, J: AUTHOR [+2]


Bridge configurations simplify AC biasing of magnetoresistive (MR) read head elements.

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AC Bias of Magnetoresistive Head

Bridge configurations simplify AC biasing of magnetoresistive (MR) read head elements.

In Fig. 1, a generalized impedance bridge driven by a carrier frequency through a transformer T1, is varied as a function of a magnetic field intersecting the elements ZH1 and ZH2. The carrier frequency may be on the order of several times the magnetic field frequency (the latter frequency may be as high as 10-30 MHz). The elements Z1, Z2, ZH1 and ZH2 form a balanced bridge which ideally removes the carrier frequency signal. A transformer T2 connects the signal to a low-pass filter which removes any carrier frequency component present. Ultimately, a signal amplifier supplies an output corresponding to the original magnetic field.

Head elements made of magnetoresistive material may be provided for components ZH1 and ZH2 of the bridge. Components Z1 and Z2 may be a pair of resistors, a pair of capacitors or a pair of mutually coupled inductors. If desired, a capacitor C may be inserted in the primary of transformer T1, as shown in Fig. 2, to form a series of resonant circuits at the carrier frequency. Fig. 3 illustrates how a single transformer may combine the functions of bridge components Z1 and Z2 and transformer T2. Capacitors may also be provided in series with components Z1 and Z2 to form resonant circuits at the magnetic field frequency. The windings of the transformers T1 and T2 may be made relatively movable if the bridge is part of a rot...