A 133.3 dB Dynamic Range Pulse Oximeter Front-End with Low-Noise Area-Efficient Offset Cancellation Current DAC

This paper introduces a pulse oximeter front-end with low-noise area-efficient offset cancellation current digital-to-analog converter (DAC). The proposed offset cancellation current DAC is implemented to cancel the input DC current to improve the effective dynamic range (DR). The current DAC is designed to have low-noise and area-efficient characteristics by applying the dynamic element matching technique and reducing the number of idle current mirror transistors. It can generate a current of up to 256 μA. Due to the offset cancellation of the current DAC, the proposed pulse oximeter has a signal-to-noise ratio of 77.4 dB and an effective DR of 133.3 dB. The pulse oximeter front-end is designed in 0.13 μm CMOS and consumes 307.1 μW from a 1.65 V supply. The figure-of-merit is 0.81 pJ/Sample.

I. Introduction

In recent years, various wearable devices that can monitor health status have been developed as interest in health problems increases due to the influence of pandemics [1]. Almost all the latest smart wearables and fitness trackers support pulse oximeters. A pulse oximeter is a non-invasive method to monitor blood oxygen saturation and pulse rate in real time. The pulse oximeter illuminates the skin and measures the amount of reflected light to obtain oxygen saturation [2].