Readout circuits for hot-wire carbon dioxide sensors in CMOS technology

This thesis describes the design and realization of CMOS-compatible CO2 sensors based on thermal conductivity (TC) measurement for indoor air-quality sensing. The goal of this work is to investigate the advantages and limitations of sensing CO2 based on TC measurement, and to exploit its potential to achieve the best possible performance in terms of both CO2 resolution and energy efficiency. Both system-level and circuit-level techniques have been explored, resulting in three prototypes that demonstrate the effectiveness of the proposed techniques. The final prototype, using a time-domain readout approach, achieves a CO2 resolution better than 100 ppm while consuming only 12 mJ per measurement, representing the best-reported performance for a CMOS CO2 sensor in terms of both resolution and energy consumption.