使用可調式主動元件及接地電容設計之低通濾波電路

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

姚清松(Ching-Sung Yao)

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/cycu200600224

摘要

摘　　　　　要
當前積體電路(IC)的製作技術無法將電容製作的很精準，使得電路的輸出訊號產生相當大的誤差，這是目前IC製作上的嚴重問題。所以尋求可調元件取代電容以實現轉移函數中s項的的作用，成為一個重要的研究方向。過去經常被使用的運算放大器(Operational Amplifier；簡稱OA)其輸出入的關係式如下 式中的A0為增益大小，ω0為頻帶寬，B0為增益及頻帶寬的乘積。由上式可知，運算放大器也可以實現轉移函數中s項的作用。本論文首先旨在研究運算放大器的B0，是否像運算轉導放大器(Operator Transconductance Amplifier；簡稱OTA)中的轉導値一樣可調?經研究結果顯示，運算放大器中的B0隨偏壓電流的增加而近似指數函數上升，並隨補償電容的增加而呈現指數函數下降的趨勢，這個重大的發現解決了電容無法製作得很精準所產生輸出誤差的問題。

本論文之設計方法，皆以YV=I之矩陣關係式開始，經由矩陣方程式的尋優，設計出一低通濾波電路，使用了一個可調的OTA，一個可調的OA及一個接地電容，為了驗證電路的可行性，使用TSMC035製程參數設定配合軟體Hspice進行模擬所得的實際值，與Matlab軟體所得之理論值比較，再利用敏感度分析模擬，在模擬的過程中，利用B0和gm的可調性，分別以±10%來調整OA及OTA內部的偏壓電流，觀察其變化結果，利用這些模擬出來的結果，成功的將電容製作時會產生的輸出頻率最大誤差由23.6944%，經由可調的OA和OTA調整到0.0102%，可以說相當的精準，最後以Butterworth準則，設計輸出頻率為10MHz的二階濾波電路，其實際值與理論值誤差為0.115%，也相當的精準，這些都可驗證B0的可調性以及本論文電路以OA來代替一個電容來實現轉移函數中s項的可行性，相信可以提供一個新的設計電路方法，一個新的設計理念。

關鍵字

低通濾波電路 ； 可調式主動元件 ； 接地電容

並列摘要

Abstract

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 function. The input-and-output relationship of an Operational Amplifier (OA) is shown as below
in which A0 is the gain, ω0 the bandwidth, and B0 the product of both gain and bandwidth. It is exhibited that an OA can also be used to realize the s terms in transfer functions. Hence, “the question is is the B0 variable, as the transconductance of anOTA, or not? ”In this thesis, we have found that the B0 is variable tuning either the bias current or the inner compensation capacitance of an OA just like the variation of the transconductance of an OTA through the tuning of its bias current. Therefore, the capacitor with error fabricated in the integrator circuit 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 low-pass filtering signal in this thesis. Finally, the H-spice simulation with 0.35μm process verifies the theoretical predictions.

並列關鍵字

Grounded Capacitor ； Low-pass Filter ； Adjustable Active elements

參考文獻

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