Towards high-dynamic range CMOS integrated interface circuits for gas sensors

This paper summarizes the results of our research activity in the field of gas-sensing systems, with particular focus on high dynamic-range (DR) integrated interface circuits. This activity was stimulated and strongly encouraged by Prof. Arnaldo D’Amico over the last ten years. The availability of large DR integrated interface circuits is absolutely necessary to turn metal-oxide chemoresistive sensors into effective gas-sensing systems. In this paper we overview different techniques for achieving read-out circuits with DR spanning from 140 dB to 160 dB and we present the experimental results obtained from three different test chips. The first and the second test chips implement a multi-scale auto-ranging read-out circuit and an oscillator-based read-out circuit, respectively, while the third test chip implements a complete gas-sensing system, including a sensor temperature control circuit as well as an oscillator-based read-out circuit. The results achieved demonstrate that metal-oxide chemoresistive sensors in combination with suitable integrated interface circuits are promising candidates for realizing low-cost portable gas-sensing systems.