Circuit and method to compensate for RMR variations and for shunt resistance across RMR in an open loop current bias architecture

Abstract

The present invention discloses a circuit ( 10 ) adapted to compensate for RMR variations and shunt resistance across the RMR comprising a first current source (idc 1 ) coupled to a first resistor (r 1 ), a second current source (idc 2 ) coupled to a second resistor (r 2 ), wherein the first resistor (r 1 ) and the second resistor (r 2 ) are coupled, a resistive sensor (RMR) coupled on either side to a third resistor (r 3 ) and to a fourth resistor (r 4 ), and a transconductance feedback block (GM) coupled to the resistive sensor (RMR), the third resistor (r 3 ), and to the fourth resistor (r 4 ).

1 . A circuit adapted to compensate for RMR variations, comprising: 
 a first current source coupled to a first resistor;    a second current source coupled to a second resistor, wherein the first resistor and the second resistor are coupled;    a resistive sensor coupled on either side to a third resistor and to a fourth resistor; and    a transconductance feedback block coupled to the resistive sensor, the third resistor, and to the fourth resistor.    
   
   
       2 . The circuit of  claim 1  further comprising a first closed loop buffer coupled to the third resistor and to the transconductance feedback block.  
   
   
       3 . The circuit of  claim 2 , wherein the first closed loop buffer is further coupled to the first current source and to the first resistor.  
   
   
       4 . The circuit of  claim 1  further comprising a second closed loop buffer coupled to the fourth resistor and to the transconductance feedback block.  
   
   
       5 . The circuit of  claim 4 , wherein the second closed loop buffer is further coupled to the second current source and to the second resistor.  
   
   
       6 . The circuit of  claim 1  further comprising a first ground coupled to the first resistor and to the second resistor.  
   
   
       7 . The circuit of  claim 1  further comprising a second ground coupled to the first current source and to the second current source.  
   
   
       8 . A circuit adapted to compensate for shunt resistance across a resistive sensor, comprising: 
 a first current source coupled to a first resistor;    a second current source coupled to a second resistor, wherein the first resistor and the second resistor are coupled;    a resistive sensor coupled on either side to a third resistor and to a fourth resistor;    a transconductance feedback block coupled to the resistive sensor, the third resistor, and to the fourth resistor; and    a shunt resistor coupled to the resistive sensor, the third resistor, and to the fourth resistor.    
   
   
       9 . The circuit of  claim 8  further comprising a first closed loop buffer coupled to the third resistor and to the transconductance feedback block.  
   
   
       10 . The circuit of  claim 9 , wherein the first closed loop buffer is further coupled to the first current source and to the first resistor.  
   
   
       11 . The circuit of  claim 8  further comprising a second closed loop buffer coupled to the fourth resistor and to the transconductance feedback block.  
   
   
       12 . The circuit of  claim 11 , wherein the second closed loop buffer is further coupled to the second current source and to the second resistor.  
   
   
       13 . The circuit of  claim 8  further comprising a first ground coupled to the first resistor and to the second resistor.  
   
   
       14 . The circuit of  claim 8  further comprising a second ground coupled to the first current source and to the second current source.  
   
   
       15 - 32 . (canceled)  
   
   
       33 . A method for compensating for shunt resistance across a resistive sensor, comprising: 
 producing a first voltage at an output node of a first closed loop buffer;    producing a second voltage at an output node of a second closed loop buffer;    applying the first voltage and the second voltage across a serially coupled resistor, a resistive sensor, another resistor, and a shunt resistance wherein the resistor is coupled to the first closed loop buffer, the other resistor is coupled to the second closed loop buffer, and the shunt resistance is coupled in parallel to the serially coupled resistors; and    increasing a current through the resistive sensor to increase a current shunted away from the resistive sensor by the shunt resistance.