臺灣博碩士論文加值系統

本研究針對生物電阻抗系統設計多通道之電流產生器，生物電阻抗系統即是利用生物阻抗特性，由外部加入多通道的交流電流，並量測其電壓值，利用所得之多組阻抗值，經過影像重建的演算法，即可得到一截面影像。而生物電阻抗系統中，注入電流的電流產生器扮演了非常重要的角色，電流產生器有兩個重要的特性：（1）輸出的電流必須穩定不受負載效應的影響，（2）各通道的電流產生器必須有相同的特性。在過去的研究，電路是以電子電路的個別元件所組成，體積龐大，且需花費時間做微調來達到各個通道的電流產生器特性一致之要求。因此，本研究主要以VLSI的技術，實現多通道的電流產生器於單一晶片上，以期特性之一致。就單一電流產生器而言，電路架構包含了兩個部分，分別是電壓控制電流源和數位類比轉換器；其中電壓控制電流源由三個運算放大器構成一負回授穩流電路，使輸出電流不受到負載效應的影響；數位類比轉換器將由數位震盪器所提供的載波，轉換成電壓控制電流源所需要的交流電壓，且透過數位輸入得到不同大小振幅的電壓。在本研究中，多通道之電流源係共用一個數位類比轉換器，因此架構上每組電壓控制電流源必須加上類比儲能元件和類比乘法器，以達成實現多通道電流產生器於單一晶片的目標。本研究使用Hspice電路模擬軟體，並依據台積電(TSMC) 0.25μm CMOS 之製程參數來驗證每個電路。

In this study, the multi-channel current generators are designed and developed for bio-impedance system. According to the characteristics of tissue impedance, by injecting AC current into the creature tissue, measuring voltages and running the image reconstruction algorithm, the functional image of creature tissue can be obtained. There are two major properties of current generator: (1) the amplitude of the current generator must be stable and independent on loading effect. (2) the property of each current generator must be the same. In past study, the current generator is composed of discrete components. The disadvantage of the traditional analog device is the worst accuracy of the values of resistances and capacitors. It always needs to fine-tune to satisfy the same property of each current generator. It also needs large volume. Therefore, the aim of the study is to realize multi-channel current generators in signal IC to ensure the similarity of property. For single channel current generator, the system consists of voltage controlled current source (VCCS) and digital to analog converter (DAC). The VCCS with feedback network is used to realize the steady current source. The DAC converts the carrier provided from digital oscillator to AC voltage for VCCS. And various amplitude of voltage is gotten by giving digital input. For multi-channel current generators, the DAC must be shared for every channel VCCS. Therefore, it is needed to add an analog storage and analog multiplier for each VCCS to accomplish the purpose of multi-channel current generators in single chip. In this study, all of the functional blocks have been verified by using Hspice according to the parameters of TSMC 0.25μm CMOS process.

中文摘要 I
Abstract II
ACKNOWLEDGEMENT IV
Table of Contents V
List of Figures VII
List of Tables IX
Chapter 1 Introduction 1
1.1 Background 1
1.1.1 Electrical impedance tomography (EIT) 1
1.1.2 Current generator for EIT system 2
1.2 Literature review 3
1.2.1 EIT system in our laboratory 3
1.2.2 Digital-to-analog converter 4
1.2.3 Analog multiplier 6
1.3 Motivation and purposes 7
Chapter 2 Materials and methods 9
2.1 System overview 9
2.1.1 Original structure of single channel current generator 9
2.1.2 Multi-channel current generators 10
2.2 IC design flow 12
2.3 Circuit design 14
2.3.1 Voltage controlled current source 14
2.3.2 CMOS R-2R ladder digital-to-analog converter 16
2.3.3 Analog storage 20
2.3.4 Analog multiplier 22
Chapter 3 Results 28
3.1 Two stage operational amplifier 28
3.2 Voltage-controlled current source 33
3.3 Digital-to-analog converter 34
3.4 Analog storage 40
3.5 Analog multiplier 42
Chapter 4 Discussion and Conclusion 47
4.1 Discussion 47
4.2 Conclusion 49
4.3 Prospects 50
References 52
自述 56

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