應用於神經訊號記錄之六十五奈米互補式金氧半八通道類比前端電路

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。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，研究與記錄下這些生理訊號是不可缺少的，而類比前端放大器電路就是從身體上取出他們的關鍵角色。 由於生理訊號有低頻、低振幅等特性，一個能夠適當放大生理訊號的前端電路必須要有高增益、低雜訊的特性，本論文設計一個八通道之類比前端放大電路以同時觀察八組電極所接收到的訊號，前置放大器為所提出之時間常數提升放大器架構，以降低低頻截止頻率於0.8Hz，防止電極直流偏移電壓被放大使輸出飽合，高頻截止頻率為可程式化之0.99KHz到4.21KHz間，而放大增益為可程式化之43/52.9/62.9 dB，以接收不同的生理訊號，像是腦皮層電圖 (ECoG)、肌電圖(EMG)和心電圖(ECG)。輸入參考雜訊為6.86μVrms，而雜訊效率因子(NEF)為5.9。本類比前端放大電路在台灣積體電路製造股份有限公司的幫助下以65奈米製程實現。 由於本電路在量測上面共模拒斥比為48.6、頻寬為4.21KHz不在規格內，本電路在重新設計後，模擬的共模拒斥比增為79.3dB，頻寬增為7KHz。

This paper presents an 8-channel analog front-end (AFEA) circuit for neural recording systems. Eight pre-amplifiers, a multiplexed transconductor and a transimpedance amplifier are designed. This AFEA is for different type of bio-potential signals, such as s electrocorticogram (ECoG), electrocardiogram (ECG) and electromyogram (EMG). For the purpose of recording different type of bio-potential signals, the gain of this AFEA is programmable 43/52.9/62.9 dB, and the bandwidth is low-pass corner is programmable 0.99k/2.33k/4.21kHz.To block the input offset voltage generated by electrode, the high-pass corner frequency is at 0.8Hz. The input-referred noise of preamplifiers is 6.86 μVrms and the noise effective factor is 5.9. The simulated re-designed AFEA fixes the problem of CMRR to 79.3dB and extend the highest low-pass corner to 7k Hz. The gain is 41.2/50.7/61.2 dB. The simulated input-referred noise of preamplifier is 4.46μVrms with 1.08μA current and the noise effective factor 2.13. This AFEA circuit is fabricated by TSMC 65nm CMOS process.