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Bias Method for Magnetoresistive Sensors

IP.com Disclosure Number: IPCOM000039311D
Original Publication Date: 1987-May-01
Included in the Prior Art Database: 2005-Feb-01
Document File: 1 page(s) / 11K

Publishing Venue

IBM

Related People

Camps, DP: AUTHOR [+2]

Abstract

A conventional magnetic biasing method for a magnetoresistive (MR) head element is combined with an AC biasing method to reproduce a signal spectrum free of intermingled distortion products. Magnetic bias is generally produced by a DC sense current achieved by a shunt conductor, a permanent magnet or a soft magnetic film in close proximity to the MR element. The static or DC magnetic field component causes the quiescent point of the MR element to be shifted to a linear portion of the parabolic curve of the MR transfer characteristic. Then a high frequency sinusoidal waveform is superimposed on the DC field through the sense conductors to the MR element. The DC sense current prevents crossing of the zero field point. For operation, the signal field to be read from the media must be less than one-third of the AC bias frequency.

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Bias Method for Magnetoresistive Sensors

A conventional magnetic biasing method for a magnetoresistive (MR) head element is combined with an AC biasing method to reproduce a signal spectrum free of intermingled distortion products. Magnetic bias is generally produced by a DC sense current achieved by a shunt conductor, a permanent magnet or a soft magnetic film in close proximity to the MR element. The static or DC magnetic field component causes the quiescent point of the MR element to be shifted to a linear portion of the parabolic curve of the MR transfer characteristic. Then a high frequency sinusoidal waveform is superimposed on the DC field through the sense conductors to the MR element. The DC sense current prevents crossing of the zero field point. For operation, the signal field to be read from the media must be less than one-third of the AC bias frequency. The signal frequencies must be of a range that the signals can be filtered and detected. The distortion products are contained within a bandwidth frequency of four times the signal frequency and centered about the origin. A bandpass filter can be used to eliminate this distortion product leaving the signal field clean of distortions.

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