Methods and apparatus for measuring analytes using large scale fet arrays

Abstract

A semiconductor device, comprising a first field effect transistor (FET) connected in series to a second FET, and a third FET connected in series to the first FET and the second FET. The semiconductor device further includes bias circuitry coupled to the first FET and the second FET, and an output conductor coupled to a terminal of the second FET, wherein the output conductor obtains an output signal from the second FET that is independent of the first FET.

What is claimed is: 
     
         1 . A method for measuring a signal from a semiconductor device comprising:
 coupling concurrently a first and a second chemically sensitive field effect transistor (chemFET) connected in series to readout circuitry in response to a select signal;   biasing the first chemFET in saturation mode;   biasing the second chemFET with a drain voltage effecting drain induced barrier lowering or punch through; and   measuring a signal from the first chemFET without interference from a signal from the second chemFET.   
     
     
         2 . The method of  claim 1 , further comprising:
 outputting a signal for a reaction occurring in a reaction region coupled to the first chemFET.   
     
     
         3 . The method of  claim 2 , wherein the reaction occurring in the reaction region coupled to the first chemFET is a nucleotide incorporation reaction. 
     
     
         4 . The method of  claim 1 , further comprising:
 biasing the second chemFET in saturation mode;   biasing the first chemFET with a drain voltage effecting drain induced barrier lowering or punch through; and   measuring a signal from the second chemFET without interference from a signal from the first chemFET.   
     
     
         5 . The method of  claim 4 , wherein the first chemFET and the second chemFET each are coupled to a corresponding hydrogen ion-sensitive layer, further comprising:
 outputting a first signal for a first reaction occurring proximal to the hydrogen ion-sensitive layer coupled to the first chemFET; and   outputting a second signal for a second reaction occurring proximal to the hydrogen ion-sensitive layer coupled to the second chemFET.   
     
     
         6 . The method of  claim 5 , wherein the first reaction and the second reaction of the first chemFET and second chemFET, respectively, is a nucleotide incorporation reaction. 
     
     
         7 . A method for operating a sensor device comprising:
 generating a row select signal by a row decoder of a chemical detection circuit, wherein the chemical detection circuit includes a chemical sensor comprising:
 a first and a second chemically-sensitive field effect transistor (chemFET) connected in series; and 
 a third FET operating as a switch; said third FET connected in series with the first and the second chemFET; 
   applying a select signal to the third FET to concurrently couple the first and the second chemFET to readout circuitry;   biasing the first chemFET in saturation mode; and   masking a signal from the second chemFET by applying a drain voltage effecting drain induced barrier lowering or punch through.   
     
     
         8 . The method of  claim 7 , further comprising:
 measuring a signal resulting from a reaction occurring proximal to a hydrogen ion-sensitive layer coupled to the first chemFET without interference from a signal from the second chemFET.   
     
     
         9 . The method of  claim 8 , wherein the reaction occurring proximal to a hydrogen ion-sensitive layer coupled to the first chemFET is a nucleotide incorporation reaction. 
     
     
         10 . The method of  claim 7 , further comprising:
 biasing the second chemFET in saturation mode; and   masking a signal from the first chemFET by applying a drain voltage effecting drain induced barrier lowering or punch through.   
     
     
         11 . The method of  claim 10 , wherein the first chemFET and the second chemFET each are coupled to a corresponding reaction region, further comprising:
 outputting a first signal for a first reaction occurring in the reaction region coupled to the first chemFET; and   outputting a second signal for a second reaction occurring in the reaction region coupled to the second chemFET.   
     
     
         12 . The method of  claim 11 , wherein the first reaction and the second reaction of the first chemFET and second chemFET, respectively, is a nucleotide incorporation reaction.