本論文主要研究慣性感測器之微電容感測電路，用於汽車中安全氣囊或導航系統中訊號的感測，由於所感測的電容訊號極微小(10-15F)，故需要一能抵抗雜訊、高準確度的電路系統來作感測。論文中說明四種常見的感測電路，並且說明電路上的不理想特性及來源，以及如何改善，經由分析後，我們選擇以差動輸出的方式作為微電容感測電路的架構，原因是此架構可以消除共模的雜訊及電路中的雜散電容且架構簡單。而設計一之電路系統由兩匹配的微電容感測電路及抗雜訊的差動放大器所組成，輸入訊號由兩組相位相反的時脈訊號來控制。設計二之電路是由兩匹配的感測電路及二級高增益放大器所構成，並提出電容匹配及抵抗雜訊之保護環佈局技術來降低誤差源。
而經由HSPICE電路模擬得知設計一的電路其輸出增益為19V/pF，總輸出雜訊約為1.26 mV，故可以得知電路最小可感測的電容值約為0.7fF；測試結果顯示電路的解析度約為50~100fF，其誤差來源為製程不匹配及測試時雜訊所造成的。而設計二的電路經HSPICE模擬得到輸出增益為190V/pF，總輸出雜訊約為2.7386 mV，故可以得知電路最小可感測的電容值約為10 aF。

This thesis researched the micro-capacitive sensing circuit for inertial sensor which used to sense poor signal in air bag or navigation. Due to the sensing capacitive signal was extremely small (10-15F), so it needed a noiseless and a high precision circuit for sensing. Thesis introduced typically four type sensing circuit , analyzed the source of nonideal effect and improvement. We chose the differential type of sensing circuit, because this architecture could cancel the common mode noise, stray capacitance and easy to analysis. The first generation of circuit design included of two matching micro-capacitive sensing circuit , noiseless differential amplifier and the input were controlled by two out of phase clock signal. The second generation of circuit design included of two matching micro-capacitive sensing circuit , two stage high gain amplifier. Layout used capacitance match , guard rings to protect core circuit and lower the interfere of EM.
The simulation results of first generation circuit showed that output gain was 19V/pF and the total noise was about 1.26 mV. So that the circuit resolution was about 0.7fF, but experiment showed the circuit resolution was about 50~100fF. We knew that the error were due to noise and dc offset. The simulation results of second generation circuit showed that output gain was 190V/pF and the total noise was about 2.7386 mV. So that the circuit resolution was about 10aF.

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