摘要
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.
| 獎項日期 | 2009 |
|---|---|
| 原文 | ???core.languages.zh_TW??? |
| 監督員 | Chih-Lung Lin (Supervisor) & Bin-Da Liu (Supervisor) |