抗臨界電壓漂移與電源干擾之濾波器設計

Abstract

在高頻寬類比濾波器的應用裡，轉導電容式濾波器咸認為是一個不錯的實現方法。但由於製程漂移的關係，使得濾波器的頻率響應規格很難達到較高的精確度。傳統使用調整電路雖可改善濾波器頻率響應的精確度，但所付出的成本與複雜度也提高許多。故本論文參考過去相關文獻，提出一個電流源偏壓技巧，改善臨界電壓漂移與電源導線壓降造成電流誤差，並應用於轉導器的設計，最後利用TSMC 0.35μm Mixed Signal 2P4M製程完成三階低通濾波器之設計。經蒙地卡羅模擬結果證實，利用此方法，頻率響應的特性有顯著的改善。

The gm-C filter has been popular in high speed analog filter applications. However, to obtain accurate frequency response is not easy due to process variation. Although several tuning circuits are proposed to improve the accuracy, the cost and circuit complexity are usually very large. In this thesis, based on traditional threshold-voltage compensation method, we proposed a current source biasing technique to reduce the current error caused by inevitable threshold-voltage variation and power line IR drop. Finally we apply this technique to third order gm-C analog filter. SPICE simulations show that for 0.35-μm TSMC Mixed Signal 2P4M process with a 3.3 V power supply, filter passband frequency variation is reduced significantly.