生醫元件可程式前端放大器

Abstract

1887年，英國科學家Augustus Waller 第一次向世人發表了心電圖。1912年，俄國生理學者Vladimir Vladimirovich Pravdich-Neminsky 紀錄下腦部的電波訊號。而十九世紀末科學家也紀錄到了肌肉裡的電訊號。自從這些生理訊號一一被發現後，人類發現這些訊號和許多神經上的疾病或身體上的活動息息相關。所以深入的研究這些生理訊號變成了重要的課題。 由於生理訊號有低頻、低振幅且獨特等特性，所以訊號的放大、低雜訊且有可調性成為訊號處理的一大挑戰。本論文即為實現一個可以用於放大Electrocochleography(ECoG)、Electromyography(EMG)和Electrocardiography(ECG)等多種生理訊號的類比前端放大器，且為了能夠同時觀察多個通道，本設計使用八通道架構，此類比前端放大器包含了前級放大器，八通道多工器和可程式增益放大器。其中新架構的前級放大器可防止電極造成的直流電壓偏移飽和電路，高頻截止頻率可調於1Hz-7KHz，放大增益40 dB，輸入參考雜訊電壓在0.5 Hz到7 KHz積分範圍為 0.9 μV rms，雜訊效率因子(NEF)為1.3。 整體的類比前端放大器的放大增益為40-74.1dB，輸入雜訊在0.5 Hz-7 KHz頻段積分為5.1 μV rms，並且有很高的共模拒斥比和電源拒斥比，功率消耗446μW，在台灣積體電路製造股份有限公司與國家晶片系統中心的幫助下，此類比前端電路晶片將以0.18微米製程實現。

This paper presents an 8-channel analog front-end (AFEA) circuit for neural recording systems. An eight-channel chopper stabilized pre-amplifier, an 8-to-1 analog multiplexer, and a programmable gain amplifier are designed. It is designed for amplification of different kinds of biopotential signals, such as electrocorticogram (ECoG), electrocardiogram (ECG) and electromyogram (EMG). These biopotential signals have the characteristics of small amplitudes, low frequency and variability. The maximum gain of AFEA is 74.1dB. The high-pass corner can achieve as low as 0.8Hz and low-pass corner can be adjusted to several kilohertz to suit for different kinds of biosignals. It is fabricated in TSMC 0.18 μm CMOS process and achieves an input-referred noise of 5.1 μVrms (input referred noise of pre-amplifier is only 0.9μVrms), bandwidth up to 7 KHz while only consumes 446 μW at 1.8V power supply. And the noise efficiency factor (NEF) is only 1.3 for pre-amplifier.