A high-sensitivity CMOS biophotometry sensor with embedded continuous-time ΣΔ modulation

This paper presents a new biophotometry sensor embedding two individual building blocks, namely a low-noise sensing front-end and a 2nd order continuous-time σδ modulator (CTSDM), into a single module for enabling high-sensitivity and high energy-efficiency photo-sensing. In particular, a differential CMOS photodetector associated with a differential capacitive transimpedance amplifier (DCTIA)-based sensing front-end is merged with an incremental 2nd order 1-bit CTSDM to achieve a large dynamic range, low hardware complexity, and high energy-efficiency. The proposed optoelectronic biosensor is implemented in a 0.18-sm CMOS technology, consuming 8.23 μW from a 1.8-v supply voltage while achieving a peak SNDR of 62.5 dB, a dynamic range of 86 dB over a 50-Hz input bandwidth, a minimum detectable current of 90-/arms, and at a 25.6-KS/s sampling frequency. The proposed biosensor presents the best FOM of 0.0197 pJ/conv. among recently published biosensors.