Substrate biasing for mr devices

Abstract

A magnetic data system according to one embodiment includes at least, one reader formed above a substrate, the at least one reader further comprising a shield and a magnetoresistive (MR) sensor. A first circuit sets a voltage (Vsub) of the substrate to about a voltage (Vshield) of the shield of the at least one reader.

1 . A magnetic data system, comprising:
 at least one reader formed above a substrate, the at least one reader further comprising a shield and a magnetoresistive (MR) sensor;   a first circuit for setting a voltage (Vsub) of the substrate to about a voltage (Vshield) of the shield of the at least one reader; and   a bias circuit coupled to the at least one reader for passing an MR bias current through the MR sensor thereof, wherein the first circuit and the bias circuit do not share common leads.   
   
   
       2 . A magnetic data system as recited in  claim 1 , wherein multiple readers are present, wherein the Vsub is set to about match the Vshield of only one reader. 
   
   
       3 . A magnetic data system as recited in  claim 1 , wherein multiple readers are present, wherein the Vsub is set to about match an average Vshield of at least two readers. 
   
   
       4 . A magnetic data system as recited in  claim 1 , further comprising a second circuit coupled to the at least one reader for setting a voltage (Vshield) of the shield to about a voltage of the MR sensor. 
   
   
       5 . A magnetic data system as recited in  claim 4 , the second circuit being coupled to the bias circuit, wherein the bias circuit for passing the MR bias current through the MR sensor of the at least one reader is able to vary the MR bias current for independently adjusting the Vshield of the at least one reader to about match the Vsub. 
   
   
       6 . A magnetic data system as recited in  claim 4 , further comprising:
 a bias circuit coupled to the at least one reader for passing an MR bias current through the MR sensor thereof, wherein the bias circuit of the at least one reader includes a first bias resistor positioned between a current source and the MR sensor and a second bias resistor positioned between the MR sensor and a ground, wherein resistance values of the bias resistors are adjustable for adjusting the Vshield of the at least one reader to about match the Vsub.   
   
   
       7 . A magnetic data system as recited in  claim 1 , wherein the first circuit oscillates Vsub between two voltage levels. 
   
   
       8 . A magnetic data system as recited in  claim 1 , wherein the first circuit comprises a path to ground and a resistor between the substrate and ground. 
   
   
       9 . A magnetic data system as recited in  claim 8 , the bias circuit comprising a bias resistor, wherein the resistance to ground of the first circuit has a resistance value in a range of between about 50 and 200 times a resistance value of the bias resistor. 
   
   
       10 . A magnetic data system as recited in  claim 1 , wherein the first circuit comprises a conductive path from the shield to the substrate. 
   
   
       11 . A magnetic data system as recited in  claim 10 , wherein the first circuit further comprises a resistor formed on the conductive path and positioned between the shield and the substrate. 
   
   
       12 . A tape drive system, comprising:
 a magnetic head;   a system as recited in  claim 1  coupled to the magnetic head;   a drive mechanism for passing a magnetic recording tape over the magnetic head; and   a controller electrically coupled to the magnetic head.   
   
   
       13 . A magnetic data system, comprising:
 at least one reader formed above a substrate, the at least one reader further comprising shields and a magnetoresistive (MR) sensor, the substrate being at about a voltage (Vsub), an electrically insulative layer being positioned between the substrate and the shields;   a circuit for operatively adjusting a voltage (Vshield) of the shield of the at least one reader to about match the Vsub.   
   
   
       14 . A magnetic data system as recited in  claim 13 , further comprising a bias circuit coupled to the at least one reader for passing an MR bias current through the MR sensor thereof, and a second circuit coupled to the at least one reader for setting a voltage (Vshield) of the shield to about a voltage of the MR sensor, the second circuit being coupled to the bias circuit, wherein the bias circuit for passing the MR bias current through the MR sensor of the at least one reader is able to vary the MR bias current for adjusting the Vshield of the at least one reader to about match the Vsub. 
   
   
       15 . A magnetic data system as recited in  claim 13 , further comprising a bias circuit coupled to the at least one reader for passing an MR bias current through the MR sensor thereof, wherein the bias circuit of the at least one reader includes a first bias resistor positioned between a current source and the MR sensor and a second bias resistor positioned between the MR sensor and a ground, wherein resistance values of the bias resistors are adjustable for adjusting the Vshield of the at least one reader to about match the Vsub. 
   
   
       16 . A magnetic data system, comprising:
 a plurality of readers formed above a common substrate, each of the readers further comprising a shield and a magnetoresistive (MR) sensor;   a first circuit for setting a voltage (Vsub) of the substrate to about a voltage (Vshield) of at least one of the shields that is not in direct physical contact with the substrate;   a plurality of second circuits, each second circuit being coupled to one of the readers, the second circuit setting Vshield to about a voltage of the MR sensor.   
   
   
       17 . A magnetic data system as recited in  claim 16 , wherein the Vsub is set to about match the Vshield of only one reader. 
   
   
       18 . A magnetic data system as recited in  claim 16 , wherein the Vsub is set to about match an average Vshield of at least two readers. 
   
   
       19 . A magnetic data system as recited in  claim 16 , wherein the Vsub is oscillated between two voltage levels. 
   
   
       20 . (canceled) 
   
   
       21 . A magnetic data system, comprising:
 at least one reader formed above a substrate, the at least one reader further comprising a shield and a magnetoresistive (MR) sensor; and   a first circuit for setting a voltage (Vsub) of the substrate to about a voltage (Vshield) of the shield of the at least one reader, the first circuit comprising a voltage source in electrical communication with the substrate, the first circuit including a resistor between the voltage source and the substrate.