An EMG Interface Comprising a Flexible a-IGZO Active Electrode Matrix and a 65-nm CMOS IC

Enrico Genco (Corresponding author), Carmine Garripoli, Jan Laurens P.J. van der Steen, Gerwin H. Gelinck, Sahel Abdinia, Pieter Harpe, Eugenio Cantatore

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Abstract

In this work, a 4× 4 active electrode (AE) matrix integrated on a flexible foil substrate to monitor muscular contraction is presented. The electrodes and their front ends (FEs) (i.e., AEs) are implemented on foil in amorphous indium gallium zinc oxide (a-IGZO) thin-film transistor (TFT) technology and interfaced with a custom 65-nm CMOS chip where analog-to-digital conversion and serial transmission of data from multiple channels are performed. On-foil frequency multiplexing and conversion to current domain are used to transmit to the silicon (Si)-IC, all the signals coming from a column of electrodes via a single output. This strategy enables interfacing the 26-V-supply flexible electronics with the 1.2-V-supply CMOS IC, while reducing the number of interconnects and Si area devoted to pads. The a-IGZO FE includes an integrated switched-capacitor high-pass input filter offering a 25-40- MΩ impedance in the band of interest. Each AE on foil occupies 4× 4 mm, enabling electromyography (EMG) measurements with millimeter (mm)-range resolution. The a-IGZO amplifier in the AE, with its intrinsic bandpass response, achieves a process and temperature-insensitive 20-dB in-band gain and a 23-dB dc rejection. The back-end Si-IC can compensate variable bias currents and offsets from the flexible FE exploiting an offset-compensated trans-impedance amplifier (TIA) with 50-dB-dc rejection and negligible noise contribution. The a-IGZO FE alone achieves 20- μ A /V gain, 30-kHz bandwidth (BW), 55- μ V_ rms input-referred noise, consuming 5 mW. The system has been validated in vivo extracting the muscle fiber conduction velocity from the tibialis anterior of a volunteer.

Original languageEnglish
Article number10130814
Pages (from-to)3138-3149
Number of pages12
JournalIEEE Journal of Solid-State Circuits
Volume58
Issue number11
DOIs
Publication statusPublished - Nov 2023

Funding

This article was approved by Associate Editor Piero Malcovati. This work was supported by the Dutch Technology Foundation STW, which is part of the Netherlands Organisation for Scientific Research (NWO) and is partly funded by the Ministry of Economic Affairs, under Project 13342.

FundersFunder number
Ministerie van Economische Zaken en Klimaat13342
Nederlandse Organisatie voor Wetenschappelijk Onderzoek
Stichting voor de Technische Wetenschappen

    Keywords

    • Active-electrode (AE) matrix
    • amorphous indium gallium zinc oxide (a-IGZO)
    • biomedical circuits
    • Electrodes
    • electrohysterography (EHG)
    • Electromyography
    • electromyography (EMG)
    • flexible matrix
    • Frequency division multiplexing
    • Iron
    • Multiplexing
    • Silicon
    • Thin film transistors

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