High Dynamic Range Photocurrent Sensory Circuit with a Multi-Transistor Background Light Cancellation Loop for Photoplethysmography Sensing

Mohamed Atef,Falah Awwad,Moien A B Khan,Osman Hassan

doi:10.3390/electronics10222769

Abstract

In this article, we present a new photocurrent sensory circuit with a three-transistor background light cancellation. We describe our innovative photocurrent sensor-based blood pressure measuring device using a resistor-based current-to-voltage converter with a background light cancellation (BLC) loop. The photocurrent sensor is implemented using 0.35 μm standard CMOS technology and has zero average power consumption. The post-layout simulation for the photocurrent sensor shows a 1.3 MΩ transimpedance gain, a referred input noise current of 11 pA, and can reject a DC photocurrent up to 200 μA. This high DC rejection has been achieved due to the newly proposed multi-transistor BLC loop integrated with the sensor.

Highlights

Introduction for Photoplethysmography SensingOptical sensing and its acquisition circuits are gaining great interest, in biomedical applications [1]
The state-of-the-art transimpedance amplifier (TIA) topologies that have been studied and presented in the literature try to optimize power consumptions, sensitivities, and bandwidths depending on the usage of different applications [9]
The proposed design succeeded in reaching a higher dynamic range and better noise performance in comparison to other recently published works

Summary

Background

Photoplethysmography (PPG)based monitoring devices allow physicians to monitor heart rate, oxygen saturation level, and blood pressure without the need for invasive procedures [1,2]. This PPG sensing technique has helped in reducing costs and speeding up the diagnostic process [3,4,5]. PPG sensors utilize a photodiode to convert the received optical power from human tissue into a photocurrent. The new proposed sensor with 3T-BLC performs better in terms of power, noise, and dynamic range than other state-of the-art topologies. Simulation, layout, and comparisons to state-of-the-art topologies are included for the proposed photocurrent sensory circuit

The Proposed 3T-BCL Photocurrent Sensory Circuit

Photocurrent Sensory Circuit Simulation

Transimpedance Amplifier Layout and Literature Comparison

Findings

Conclusions