A trapped charge compensation scheme for ISFET based translinear circuits

A trapped charge compensation scheme for ISFET based translinear circuits is presented, as part of a system for prediction of cancer risk, based on DNA methylation. Each pixel is able to measure a DNA methylation ratio through pH-based measurements and by using in-pixel comparison to a tunable threshold, to output a result which indicates percentage of methylation used as a cancer score. The developed system was designed in a 0.35 μm CMOS technology and uses a novel trapped charge compensation scheme for ISFETs used in translinear circuits. The output scheme was able to compensate trapped charge of up to 380mV, with a ratio error below 5%, in a range of ratios between 50% and 80% which is generated from pH-based DNA methylation reactions.