A single-chip integrated interfacing circuit for wide-range resistive gas sensor arrays

In this work, we present novel experimental results on a single-chip integrated interface for wide-range resistive gas sensors. The proposed circuit has been proved to be able to reveal more than five decades of resistance variation (about 1% of relative error in the range 470k Omega-50G Omega) and, at the same time, to estimate the sensor parasitic capacitance (about 0.3 pF of estimation error in the range 0-33 pF). The fabricated integrated circuit has shown good performances in a wide range of environmental temperature (from -20 degrees C to 80 degrees C). The suitability for sensor applications has been proved by interfacing a high-value resistance MOX sensor and monitoring both the resistance and the parasitic capacitance values during a fast thermal transient of the sensor. Moreover, the front-end has been utilized, as an example, for the detection of hydrogen by means of a Figaro TGS 2600 sensor. An on/off modulation has been applied during the fluxing of two gas mixtures, constituted by both hydrogen and nitrogen, with a hydrogen concentration of 40 ppm and 80 ppm. respectively. Compared to other solutions presented in the literature, the implementation and fabrication as integrated circuit in a standard CMOS technology allows the whole interface to be considered as a simple and low-cost solution for wide-range resistive sensor arrays. (C) 2009 Elsevier B.V. All rights reserved.