A sub-nanoampere current differentiator

A novel current differentiator capable of differentiating a step current with step size as low as 50 pA is described. It requires only four MOSFETs and consumes less than 10/sup -8/ W power. This makes the novel current differentiator, called the current-mirror (CM) differentiator, a suitable building block for the implementation of motion-detecting imagers with medium pixel density ( approximately=60 pixels/mm/sup 2/). The circuit has been implemented using 3 mu m CMOS technology.<>