Auto‐clamping interface circuit for high electron mobility transistor‐based heavy metal detection sensor

Abstract

SummaryIn this paper, we present an improved full Wilson current mirror‐based interface system, which utilizes an auto‐balancing technique, for High Electron Mobility Transistor (HEMT)‐based biochemical sensors. The auto‐tuning technique maintains a constant voltage across the sensor and simultaneously provides an output voltage proportional to the measurand. The proposed circuit is particularly useful for HEMT‐based sensors with large offset current since the design performs base current compensation. The design and analysis of the proposed circuit are verified experimentally on a prototype Printed Circuit Board (PCB). The effectiveness of the circuit is proven by carrying out repeated experiments for evaluating linearity, accuracy, and standard deviation. The obtained result of the prototype shows that the proposed circuit is able to work from 300 Ω to 2.1 kΩ with a relative error of less than ±2%. The prototype is finally tested with an in‐house fabricated HEMT‐based heavy metal sensor. The measurement range of the proposed circuit is tunable according to the sensor operating range, which enables the potential use of the proposed circuit for a wide range of HEMT‐based sensors.