截波穩定運算放大器結合線性陣列型生物感測器前端讀出電路積體化設計與實現

本論文的研究在於結合線性陣列型酸鹼感測器與讀出電路來完成訊號讀取，主要以訊號處理、雜訊分析、電路設計的考量及介面之間關係做研究；從以往使用玻璃參考電極改成使用銀膠參考電極感測，繼而將銀膠參考電極結合陣列式生物感測器，其優點可達多功能感測、同時進行多比量測增加量測效率及可提高使用率，並證實使用陣列型生物感測器可提高訊號雜訊比；電路方面證明截波技術可降低輸入偏移電壓和偏移電壓的漂移且隨著截波頻率越快輸入雜訊可越小，適用於感測微小訊號的低頻生物感測器，整個讀出電路設計子電路包含：類比多工器、截波穩定運算放大器、凖位調整器、濾波器及電壓隨耦器，其中放大器均採用摺疊式疊接(Folded Cascade)架構設計，再透過國家晶片中心(chip-implementation-center , CIC)以TSMC 0.35um 2P4M CMOS標準製程做全客戶設計，並使用商業IC量測子電路特性規格；讀出電路設計規格以酸鹼量測為主，量測範圍為pH2至pH12。

關鍵字

線性陣列；類比多工器；截波穩定運算放大器；摺疊式疊接；訊號雜訊比

並列摘要

This study investigated the performance of our newly-designed readout circuit on linear array pH sensor. From this research, I learned signal processing, circuit design, interface relationship between sensor and readout circuit, and noise analysis. The experimental procedures were that silver reference electrode, substituted the traditional glass reference electrode, was used together with a single pH sensor for pH measurements in order to prove the silver electrode could be used as a reference electrode. Then, the silver reference electrode was used together with the linear array pH sensor for pH measurements. The advantages of using linear array sensor were multi-sensing of analytes at the same time, still workable even several sensors of the linear array sensor were damaged, and higher signal to noise ratio. In this study, a readout circuit for the linear array pH sensor was designed and developed, using chopper stabilization technique. It consisted of analog multiplexer, chopper stabilized operational amplifier, level shift, filter and buffer stage. The operational amplifier used in this design was a folded cascade amplifier. It was found that the circuit could reduce input offset, drift voltage and noise and noise could be further reduced on a faster chopper frequency. This readout circuit could be used for measuring small signal of low frequency biosensor. The finalized readout circuit design was then implemented through the chip-implementation-center (CIC) using TSMC 0.35um 2P4M standard CMOS process. In conclusion, a readout circuit utilizing chopper stabilization technique was designed and developed in this study. The readout circuit used together with the linear array pH sensor were able to have a measurement range of pH2~pH12.