Charge measurement

Abstract

An apparatus comprises a comparator that includes a first input, a second input and an output. The comparator is configured for measuring a difference in voltage between a source coupled to the first input and another source coupled to the second input, and providing information associated with the measured difference at the output. The apparatus also comprises a controllable current source coupled to the first input of the comparator and configured for supplying or drawing current. The apparatus also comprises a digital logic circuit that is configured for controlling an amount of current supplied or drawn by the controllable current source. The apparatus is configured for measuring a charge associated with an external source that is coupled to the first input of the comparator.

What is claimed is: 
     
         1 . An apparatus comprising:
 a comparator including a first input, a second input and an output, the comparator being configured for measuring a difference in voltage between a source coupled to the first input and another source coupled to the second input, and providing information associated with the measured difference at the output of the comparator;   a controllable current source coupled to the first input of the comparator and configured for supplying or drawing current; and   a digital logic circuit coupled to the output of the comparator and to an input of the controllable current source, the digital logic circuit being configured for controlling an amount of current supplied or drawn by the controllable current source,   wherein the apparatus is configured for measuring a charge associated with an external source that is coupled to the first input of the comparator.