A Programmable, Highly Linear and PVT-Insensitive ISFET Array for PoC Diagnosis

Abstract

This paper presents a novel 32×32 ISFET array for DNA amplification detection. Each pixel contains a highly-linear ISFET-based OTA and a sawtooth oscillator, converting the solution pH into a digital clock with chemically controlled duty cycle. By employing a differential measurement between a DAC-generated voltage and the pH solution on the OTA, a highly linear, PVT-insensitive response is achieved, while opening the possibility of real-time pixel-wise compensation of trapped charge and chemical drift. The proposed architecture achieves a sensitivity of 11.78%/pH while maintaining large linear dynamic range and a temperature sensitivity of 0.0033 pH/K. Implemented using 0.18μm standard CMOS technology, each pixel occupies 40 μm × 40 μm. This architecture paves the way towards a new generation of ISFET imagers, capable of learning from data and correcting their measurements in real time.