可自行校正精確度的電流源設計

Abstract

電流式數位類比轉換器(current mode DAC) 乃由電流源與開關構成,本論 文提出一種有別於動態電流源複製(dynamic current copier)的靜態電流 源,而這種靜態電流源的優點乃同時擁有高速度與高準確度,而這兩種特性 很難同時擁有 。比方說動態電流源複製(dynamic current copier)的準 確度很高可是速度很低,而這種靜態電流源的缺點為消耗相當大的面積。 為了驗證我們的線路,設計了一步校正式積體電路,來產生三個校正過的電 流源 。量測結果為三個校正過的電流源輸出與輸入差約10微安,不過有 時電流比較器會判斷錯誤,這在第五章討論 。為了更準確,我們又設計了 三步校正式電路,並且模擬驗證之 。一步校正式電路與三步校正式電路在 本論文中皆詳細討論之 。 Current mode DACs (Digital-to-Analogue Converter) are composed of current sources and switches.In this thesis,a static current source which is different from the so-called 'dynamic current copier' is proposed and analyzed.The advantages of the static current source of this thesis are high speed and high resolution which can not be obtained at the same time. For example,dynamic current copiers can have very high resolution but very low speed. However,the disadvantage of this thesis is that it will inevitably consume a lot of silicon area. To test our circuits , we designed the one-step self- calibration IC to generate three calibrated current sources by the method of this thesis.Measurement results have confirmed that the three current sources had the values close to the input current which varied from 90uA to 140uA , although the chip would have wrong judgements discussed in chapter 5.In order for the calibrated current sources to be closer to the the input current , we further designed the three-step self- calibration circuit and SPICE simulations have confirmed the results.One-step and three-step calibration are fully discussed in this thesis.