An Asynchronous Auto-biasing Circuit for Wearable Electrochemical Sensors

This work presents a circuit for asynchronous, automatic biasing of a CMOS ISFET array for wearable electrochemical measurement systems. The circuit is integrated into a temperature compensated pH-to-frequency converter utilising the floating gates of an ISFET array. The work represents the first effort to address the issue of variable bias points in integrated electrochemical sensors for wearable applications, and is a low power, low transistor solution without an output voltage ripple. Designed in a 0.35μm CMOS technology, the system achieves a low power consumption of 29.72μW with a typical settling time of 0.7ms.