Magnetoresistive read head assembly having matched elements for common mode rejection

Claim 2

A magnetic read head assembly for sensing magnetically recorded information comprising: two magnetostatically coupled magnetoresistive elements, said elements having substantially the same thickness and magnetic properties; insulating means disposed between said elements for breaking the magnetic exchange coupling between said elements, and for electrically isolating one element from the other element; means for supplying a drive current concurrently to said elements so that the current through each element serves to magnetically bias the other of said elements, said elements being biased in opposite directions; and signal output means connected to said elements, including means for sensing the difference in voltage of the elements.

Claim 3

The magnetic head assembly of claim 1, wherein said means for supplying a drive current includes a constant current source.

Claim 4

The magnetic head assembly of claim 1, wherein said difference sensing means comprises a differential amplifier.

Claim 5

The magnetic head assembly of claim 1, further comprising magnetic shield means for magnetically shielding said magnetoresistive elements from magnetic fields emanating from sources other than the recorded bit of magnetic information being sensed.

Claim 6

The magnetic head assembly of claim 1, wherein said magnetoresistive elements are matched magnetically and electrically.

Claim 7

An assembly for sensing magneticallY recorded information and providing common mode rejection of noise, said assembly comprising: two matched magnetoresistive elements in close proximity to one another having substantially the same thickness and same magnetic properties, so as to be magnetostatically coupled insulating means disposed between said elements for breaking the magnetic exchange coupling between said elements, and for electrically isolating one element from the other element; and means for supplying a drive current concurrently to said elements; so that the current through each element serves to magnetically bias the other of said elements, said elements being biased in opposite directions, such that the magnetic field associated with each bit of magnetically recorded information causes resistance changes of opposite polarity in said elements, whereas thermal fluctuations and sources of noise signals produce resistance changes of identical polarity in each element whereby only the recorded bits produce a difference in voltage across said elements, and common mode rejection is provided for thermal fluctuations and noise signals; signal output means connected to said elements, including means for sensing the difference in voltage of the elements.

Claim 8

An assembly for sensing magneticallY recorded information and providing common mode rejection of noise, said assembly comprising: two matched magnetoresistive elements in close proximity to one another having substantially the same thickness and same magnetic properties, so as to be magnetostatically coupled insulating means disposed between said elements for breaking the magnetic exchange coupling between said elements, and for electrically isolating one element from the other element; and means for supplying a drive current concurrently to said elements; so that the current through each element serves to magnetically bias the other of said elements, said elements being biased in opposite directions, such that the magnetic field associated with each bit of magnetically recorded information causes resistance changes of opposite polarity in said elements, whereas thermal fluctuations and sources of noise signals produce resistance changes of identical polarity in each element whereby only the recorded bits produce a difference in voltage across said elements, and common mode rejection is provided for thermal fluctuations and noise signals; signal output means connected to said elements, including means for sensing the difference in voltage of the elements.