使用可調式主動元件及接地電容設計之低通、帶通濾波電路

Design of the Band-pass and Low-pass Filter Structure using Adjustable Active elements and a Single Grounded Capacitor

洪秋伯(Chiou-Bo Hung)

指導教授 ： 張俊明

中原大學/工學院/電機工程研究所/碩士(2006年)

https://doi.org/10.6840/cycu200600195

摘要

本論文以處理電容因製程技術所產生的誤差為出發點，尋求類似OTA般具有可調性且能夠取代電容在電路中實現s項的主動元件。經本論文研究後發現，運算放大器(Operational Amplifier,簡稱OA)恰好可用來實現電路轉移函式中的s項。再經過深入研究，更發現OA的增益頻寬乘積可以藉由改變OA的偏壓電流與內部的補償電容做調整；進而嘗試以OA取代電容器進行電路設計，提出了使用可調OA、可調OTA及接地電容的低通及帶通濾波電路。

吾人首先對IC製程中電容的誤差做了一個詳細的測試與統計，結果得到電容因為製程的關係有可能存在最大誤差-15.82%。然後以此最大誤差去模擬電容誤差對電路性能的影響，再利用可調OA與可調OTA對測試出電容所產生的誤差來進行調整，其中調整的依據為電路針對各可調參數所做的敏感度分析結果。雖然使用OA代替電容將佔用晶片中較大的面積，但卻增加了電子可調的優點。而對於電路非理想效應的部份，經由考慮非理想參數的理論分析與實際驗證與實際模擬相符合，證明了OA與OTA的頻寬的確影響了電路整體輸出的結果。

經過使用H-spice以tsmc035製程參數模擬所得到的結果，證明了以OA來實現電路中s項的功能確實能完全改善電容因IC製程所產生誤差對電路造成的影響。另外本論文所提出的電路架構也能夠實現標準的二階Butterworth濾波功能，文章中並有詳細的驗證。

關鍵字

可調式主動元件 ； 帶通 ； 低通 ； 濾波器 ； 接地電容

並列摘要

It is worthy of research to do the analogue circuit design using Operational Transconductance Amplifiers (OTAs) and Capacitors (Cs) because an OTA is equivalent to both an active element and a resistor leading to a more condensed integrated circuit without resistors ,and because the equivalent resistor value can be electronically tuned varying the bias current.
Due to the difficulty to precisely fabricate the capacitance in integrated circuits, it becomes an important research work to find a tunable element for the replacement of the capacitor used to realize the s terms in transfer functions.
It is exhibited that an OA can also be used to realize the s terms in transfer functions. Hence,”the question is ”Is the variable , as the transconductance of an OTA, or not ?”In this thesis , we have found that the is variable tuning either the bias current or the inner compensation capacitance of an OA just like the variation of the trancondance of an OTA through the tuning of its bias current. Therefore, the capacitor with error fabricated in the integrated circuits can be replaced by the OA tunable through its inner bias current.
The thesis is focused on the design of biquads using both tunable OA and tunable OTA, leading to very precise output responses such as lowpass and bandpass filtering signals. Finally, the H-spice simulation with TSMC035 process verifies the theoretical predictions.

並列關鍵字

lowpass ； adjustable active elements ； filter ； capacitor ； bandpass

參考文獻

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