Active pixel sensor (aps) readout structure with amplification

Abstract

An active pixel sensor (APS) includes an array of individually addressable APS cells ad a pixel readout structure that includes an amplifier. The amplifier may have a two-branched structure and provide a gain of one or higher. Additional switches may be provided in the pixels to provide protection for pixel output transistors from voltage changes in the column line. Structure may also be provided for optional gain selection in the amplifier.

1 - 17 . (canceled) 
     
     
         18 . A method of reading out a signal from an imager pixel in an imager device, said method comprising the acts of:
 converting photo-generated charge from a photosensor in the pixel into a first voltage;   outputting the first voltage to a first amplifier branch; and   amplifying the first voltage in a second amplifier branch to apply a gain greater than one to the first voltage.   
     
     
         19 . The method of  claim 18  further comprising the act of substantially blocking unwanted voltage changes from being applied to an output transistor located in the first amplifier branch. 
     
     
         20 . A method of reading out a signal from an imager pixel in an imager device, said method comprising the acts of:
 converting photo-generated charge from a photosensor in the pixel into a first voltage;   outputting the first voltage to a first amplifier branch;   amplifying the first voltage in a second amplifier branch to apply a first gain to the first voltage;   altering the first gain to form a second gain by connecting a gain altering element to the second amplifier branch; and   applying the second gain to the first voltage.   
     
     
         21 . The method of  claim 20 , wherein the altering step comprises enabling a gain altering element connected to the second amplifier branch. 
     
     
         22 . The method of  claim 20 , wherein the altering step comprises switching in a gain altering element into the second amplifier branch. 
     
     
         23 . A method of reading out a signal from an imager pixel in an imager device, said method comprising the acts of:
 converting photo-generated charge in the pixel into a first voltage;   outputting the first voltage to a first amplifier branch;   selecting a gain to be applied to the first voltage by connecting a gain altering element to the second amplifier branch; and   applying the selected gain to first voltage in a second amplifier branch to form an amplified voltage.   
     
     
         24 . The method of  claim 23 , wherein the selected gain is a gain greater than one. 
     
     
         25 . The method of  claim 23 , wherein the selecting step comprises switching in the gain altering element into the second amplifier branch. 
     
     
         26 . The method of  claim 23 , wherein the selecting step comprises enabling the gain altering element. 
     
     
         27 . The method of  claim 23  further comprising the act of substantially blocking unwanted voltage changes from being applied to an output transistor located in the first amplifier branch.