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 470 kOhm–50 GOhm) 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°C to 80°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.