부산대학교 도서관

Fluorescence biophotometry measurements require wide dynamic range (DR) and high-sensitivity laboratory apparatus. Indeed, it is often very challenging to accurately resolve the small fluorescence variations in presence of noise and high-background tissue autofluorescence. There is a great need for smaller detectors combining high linearity, high sensitivity, and high-energy efficiency. This paper presents a new biophotometry sensor merging two individual building blocks, namely a low-noise sensing front-end and a $2\text{nd}$ order continuous-time $\Sigma \Delta$ 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-based sensing front-end is merged with an incremental $2\text{nd}$ order 1-bit CTSDM to achieve a large DR, low hardware complexity, and high-energy efficiency. The sensor leverages a hardware sharing strategy to simplify the implementation and reduce power consumption. The proposed CMOS biosensor is integrated within a miniature wireless head mountable prototype for enabling biophotometry with a single implantable fiber in the brain of live mice. The proposed biophotometry sensor is implemented in a 0.18-$\mu \text{m}$ CMOS technology, consuming $\text{41}\ \mu \text{W}$ from a 1.8-$\text{V}$ supply voltage, while achieving a peak dynamic range of $\text{86}\ \text{dB}$ over a 50-$\text{Hz}$ input bandwidth, a sensitivity of 24 mV/nW, and a minimum detectable current of 2.46- $pA_{\rm rms}$ at a 20- $\text{kS/s}$ sampling rate.