Shield biasing for mr devices

Abstract

A magnetic data system according to one embodiment includes a head having a plurality of readers formed above a common substrate, each reader further comprising a shield and a sensor, a bias circuit associated with each reader for passing a bias current through the sensor thereof, wherein the bias circuits are floating. A charge clamp electrically couples each shield to the associated bias circuit. A shield biasing circuit is operatively coupled to each shield for setting a potential of the shield independently of the bias current.

1 . A magnetic data system, comprising:
 a head having a plurality of readers formed above a common substrate, each reader further comprising a shield and a sensor;   a bias circuit associated with each reader for passing a bias current through the sensor thereof, wherein the bias circuits are floating; and   a shield biasing circuit operatively coupled to each shield for setting a potential of the shield independently of the bias current.   
   
   
       2 . A system as recited in  claim 1 , wherein the potential of each shield is set to match about a potential of the substrate. 
   
   
       3 . A system as recited in  claim 1 , wherein the potential of each shield is set to within less than about 0.1 V of the potential of the substrate, wherein the shields are not electrically coupled to the substrate. 
   
   
       4 . A magnetic storage system as recited in  claim 2 , further comprising a substrate biasing circuit coupled to the substrate for setting the potential of the substrate. 
   
   
       5 . A system as recited in  claim 1 , wherein the potential of each shield is set to ground. 
   
   
       6 . A system as recited in  claim 1 , wherein the shield biasing circuit is integral to the head. 
   
   
       7 . A system as recited in  claim 6 , wherein the shield biasing circuit is electrically coupled to the substrate. 
   
   
       8 . A system as recited in  claim 1 , wherein the shield biasing circuit further comprises a resistor coupled between the shield and the substrate. 
   
   
       9 . A system as recited in  claim 6 , wherein the shield biasing circuit is coupled to a pad on the head. 
   
   
       10 . A system as recited in  claim 6 , wherein the shield biasing circuit is coupled to a bus bar of the head. 
   
   
       11 . A system as recited in  claim 1 , wherein wherein at least a portion of the shield biasing circuit is located remotely from the head. 
   
   
       12 . A system as recited in  claim 11 , wherein the shield biasing circuit further comprises two resistors coupled to each bias circuit across the associated sensor and a reference voltage source coupled between the resistors. 
   
   
       13 . A system as recited in  claim 11 , wherein the shield biasing circuit further comprises two resistors coupled across each bias circuit and a reference voltage source coupled between the resistors. 
   
   
       14 . A system as recited in  claim 11 , wherein the shield biasing circuit is electrically coupled to the substrate. 
   
   
       15 . A system as recited in  claim 1 , wherein the same shield biasing circuit is operatively coupled to all of the shields. 
   
   
       16 . A system as recited in  claim 1 , wherein multiple shield biasing circuits are present, each shield biasing circuit being operatively coupled to one of the shields. 
   
   
       17 . A system as recited in  claim 1 , further comprising a charge clamp circuit electrically coupling each shield to the associated bias circuit, the charge clamp circuit coupling each shield to both leads extending from the associated sensor. 
   
   
       18 . A system as recited in  claim 1 , further comprising:
 a drive mechanism for passing a magnetic recording tape over the head; and   a controller electrically coupled to the head.   
   
   
       19 . A magnetic data system, comprising:
 a head having a plurality of readers formed above a common substrate, each reader further comprising a shield and a sensor;   a bias circuit associated with each reader for passing a bias current through the sensor thereof, wherein the bias circuits are floating;   a substrate biasing circuit for setting a potential of the substrate; and   a shield biasing circuit operatively coupled to each shield for setting a potential of each shield to about match the potential of the substrate,   wherein the shields are not coupled directly to a around.   
   
   
       20 . A magnetic data system, comprising:
 a head having a plurality of readers formed above a common substrate, each reader further comprising a shield and a sensor;   a bias circuit associated with each reader for passing a bias current through the sensor thereof, wherein the bias circuits are floating;   a circuit electrically coupling each shield to the associated bias circuit; and   a shield biasing circuit operatively coupled to each shield for setting a potential of the shield independently of the bias current,   wherein the potential of each shield is set to match about a potential of the substrate, wherein at least one of the shields is not electrically coupled to the substrate.