本論文實現一應用於生醫濃度感測之伏安式恆電位儀電路。其電路原理為設法固定兩測試電極的電位差，利用不同待測溶液濃度造成不同的等效電阻之特性，以產生一隨溶液濃度變化的電流。藉由一電流模式之增值型三角積分調變器感測此類比電流並將其轉成1 bit之數位訊號，之後透過一個16-bit計數器將此1 bit之數位訊號轉換成16-bit之數位訊號，根據數位碼的大小推估溶液濃度。由於此調變器電路直接對電流進行訊號處理，因此，可避免電流轉電壓等訊號轉換所造成的失真。為了達到寬廣的電流量測範圍，採用增益調變技術，改變調變器內數位至類比轉換器之操作頻率。此外，利用超取樣方式，達到更高之準確度。
本論文使用0.35 um二層多晶矽金屬之互補式金氧半製程，實現供應電壓為5 V之伏安式恆電位儀，其感測電流範圍可達10 pA~10 uA，準確度可達10 bits，不含後級計數電路，整體電路消耗為4.22 mW。

In this thesis, a potentiostat circuit for sensing bio-solution concentration is proposed. The operation principle of this circuit is to fix the voltage difference between two measuring electrodes. The equivalent resistance of the solution under measurement is strongly related with the solution concentration. Therefore, a solution concentration dependent current would be produced. A current mode incremental sigma-delta modulator is used to sense and transform this analogous current into one bit digital stream. This bit stream is transformed as 16-bit digital codes by a 16-bit counter. Finally, we could calculate solution concentration from the relationship of the digital code and solution concentration dependent current. Since the modulator directly processes the current signal, it could avoid the distortion due to additional transconductance amplifier. Moreover, in order to obtain a wide range of sensing current, we adopt gain modulation technique to adjust the integrated time of the integrator and the turn-on time of the feedback current digital-to-analog converter (DAC). Furthermore, a oversampling technique is also employed to improve the circuit accuracy.
This work is implemented in a TSMC 0.35 um 2P4M CMOS process from 5 V supply voltage. The range of sensing current is from 10 pA to 10 uA, and the resolution is up to 10 bits. The total power consumption is 4.22 mW, excluding the back-end digital counter.

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