Method for trimming resistors

Abstract

There is provided a method and circuit for trimming a functional resistor on a thermally isolated micro-platform such that a second functional resistor on the same micro-platform remains substantially untrimmed; a method and circuit for providing and trimming a circuit such that at least two circuit elements of the circuit are subjected to a same operating environment and the operating environment is compensated for by distributing heat generated during operation of the circuit among the two circuit elements; a method and circuit for trimming a functional resistor on a thermally-isolated micro-platform such that a constant temperature distribution is obtained across the functional resistor; and a method and circuit for calculating a temperature coefficient of resistance of a functional resistor.

1 . A method for providing and trimming a circuit, the method comprising: 
 placing at least two resistive elements with non-zero temperature induced drift on a substrate to be thermally isolated, such that said at least two resistive elements are subjected to a substantially same operating environment, at least one of said at least two resistive elements being thermally trimmable;    trimming said at least one resistive element to trim said circuit by thermal cycling;    connecting said at least two resistive elements together in said circuit in a manner to compensate for said operating environment;    wherein heat generated during operation is distributed among said at least two resistive elements such that temperature drift is substantially compensated.    
   
   
       2 . A circuit as claimed in  claim 1 , further comprising providing at least one thermally-isolated micro-platform on said substrate, and wherein said at least two resistive elements are on said at least one thermally-isolated micro-platform.  
   
   
       3 . A method as claimed in  claim 2 , wherein said connecting said at least two resistive elements together comprises connecting said two resistive elements in series, wherein an applied voltage is divided with a predetermined ratio.  
   
   
       4 . A method as claimed in  claim 2 , wherein said placing at least two resistive elements of said circuit on said at least one thermally-isolated micro-platform comprises said at least two resistive elements to be temperature sensitive elements located closely on said at least one thermally-isolated micro-platform, and whose signals are combined to measure a temperature differential induced during operation.  
   
   
       5 . A method as claimed in  claim 4 , wherein said signals are combined to measure a temperature differential induced by a gas movement.  
   
   
       6 . A method as claimed in  claim 2 , further comprising placing a heating resistor on the at least one thermally-isolated micro-platform in close proximity to said at least one resistive element, wherein said trimming said at least one resistive element further comprises passing a signal through the heating resistor to increase its temperature significantly for the purpose of trimming said at least one resistive element.  
   
   
       7 . A method as claimed in  claim 6 , wherein said heating resistor and said at least one resistive element are on separate thermally-isolated micro-platforms.  
   
   
       8 . A method as claimed in  claim 2 , wherein said trimming comprises providing a plurality of electrical pulses and measuring said resistance value of one of said at least two resistive elements in between each of said plurality of electrical pulses to determine whether a target resistance value has been obtained.  
   
   
       9 . A method as claimed in  claim 2 , wherein said heating comprises providing dynamically-shaped electrical pulses to achieve substantially constant temperature as a function of time during a trimming pulse.