An automatic transimpedance gain control circuit for analogue front-ends of drifting amperometric biosensors

Abstract

Abstract When amperometric biosensors drift, their sensitivity drops with time: the same difference in detected concentration value Δ C results in lower sensor output current Δ I as the measurement/monitoring time progresses. This limitation affects the longevity of biosensors. To counterbalance for the drop in sensitivity, manual adjustment of the I-to-V transimpedance gain is usually applied. This paper presents an automatic transimpedance gain control circuit suitable for switched-capacitor-based current analogue front-ends. The circuit has been fabricated in the 0.35 μ m AMS technology, occupies an area of 0.028 mm 2 and consumes 14.5 μ W from a 3.3 V supply. Measured results confirm the automatic selection between three values of transimpedance gain, namely 1, 10 and 100 G Ω each optimised for sensor current range values of ±1.65 nA, ±165 pA and ±16.5 pA respectively. Though the reported topology has been tailored for glucose/lactate amperometric biosensors of slow temporal dynamics, its parameters can be made to match the conditions of other physiological/physical processes in need of monitoring.