應用於生醫訊號偵測的低功率低雜訊之互補式金氧半電流訊號前端放大器

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並且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設計的一大挑戰。本論文即為實現一個可用於放大Electrocochleography (ECoG)、Electromyography (EMG) 和 Electrocardiography (ECG) 等多種生理訊號的類比前端放大器，不同於一般的放大器都是去偵測並放大電壓訊號，我們所設計的是去偵測並放大電流訊號並利用其優點，並設計了單端輸入以及雙端輸入的放大器，此前端放大器皆包含前級放大器、可抑制低頻訊號的迴圈、可調式增益放大器、可調頻寬之濾波器、以及將電流訊號轉成電壓訊號的放大器。經過改善的雙端放大器其低頻截止頻率可低於1Hz，而高頻截止頻率可調於1K Hz到7K Hz，放大增益有52.1/ 58/ 62.9 (dB)可供調整，輸入參考雜訊電壓在 1 Hz 到10K Hz 積分範圍為1.92μVrms，雜訊效率因子(NEF)為 2.3。 並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 a single-ended-input current-mode front-end amplifier (CMFEA), and a differential-input CMFEA. The CMFEA is used for amplifying different kinds of biopotential signals such as ECoG, ECG, and EMG. These biopotential signals have the characteristics of small amplitudes, low frequency, and variability. The single-ended-input CMFEA which is fabricated in TSMC 0.18um CMOS process can adjust gain at three steps (44.5/ 50 /55.9 dB) digitally, bypass flowing-in dc offset current below 0.3Hz, and the low-pass corner of it can be tuned from 1K Hz to 10K Hz. The input-referred noise is 4.4uVrms from 1Hz to 10K Hz. The power consumption is only 13uW at 1-V power supply. And the NEF is 5.45. The differential-input CMFEA inherits the advantages of single-ended-input CMFEA. Besides, it can bypass bi-directional dc offset current. And the noise of it is smaller, and the high-pass corner of it is more insensitive to the dc offset current. The differential-input CMFEA which also is fabricated in TSMC 0.18um CMOS process can adjust gain at three steps (52.1/ 58 /62.9 dB) digitally, bypass bi-directional dc offset current below 0.5Hz, and the low-pass corner of it can be tuned from1K Hz to 7K Hz. The input-referred noise is only 1.92uVrms from 1Hz to 10K Hz. The power consumption is 12.1uW at 1-V power supply. And the NEF is 2.3.