本論文提出一個以運算轉導放大器(OTA)設計的全新ㄧ階低通平方根濾波器。此平方根濾波器的基本架構只使用一個translinear濾波器和兩個運算轉導放大器。

我們改良Cruz的平方根濾波器[15]，將原本所需的三個轉導架構化減為兩個，並使用運算轉導放大器取代AB類(Class-AB)線性轉導。它是目前使用最少電晶體數的平方根濾波器，因此有最少的功率損耗和晶片面積。

本研究使用 0.35μm CMOS 製程製作晶片，其供應電壓為1.5V，調整電流為0.05μA~15μA。外接電容1nF時的截止頻率為250Hz~29kHz，總諧波失真約1.03%，外接電容100pF時的截止頻率為1.8KHz~237kHz，總諧波失真約1.01%。功率損耗116μW。

In this thesis, a brand new first-order low pass square root domain filter (SRD filter) based on operational transconductors amplifiers (OTAs) is presented. The SRD filter consists of a translinear filter and two OTAs.

We improve Cruz’s SRD filter [15], reduce the number of transconductors from 3 to 2, and replace Class-AB linear transconductors with OTAs. The circuit has the least number of transistors up to date, therefore, the least power consumption and least chip area.

The circuit has been fabricated with 0.35μm CMOS technology. It operates with a supply voltage 1.5V and the biasing current varies from 0.05uA to 15uA. Measurement results show that the cutoff frequency of the filter can be tuned from 250 Hz to 29 kHz when the external capacitance C is 1nF and the cutoff frequency can be tuned from 1.8 kHz to 237kHz when the external capacitance C is 100pF. The total harmonic distortion is 1.03% and 1.01% when the external capacitance C is 1nF and 100pF and the power consumption is 116μW.

Abstract
Chapter 1 Introduction
1.1 Background and History
1.2 Motivation and Problem
1.3 Thesis Organization

Chapter 2 Previous SRD filter
2.1 The principle of SRD LPF
2.1.1 Translinear filter
2.1.2 The transfer function
2.2 Cruz’s SRD filter
2.2.1 Class-AB linear transconductor
2.2.2 The analysis of Cruz’s SRD filter

Chapter 3 The proposed Circuit
3.1 Modified Cruz’s SRD filter
3.2 Novel SRD filter
3.2.1 Operational transconductor amplifier
3.2.2 The proposed SRD filter

Chapter 4 Simulation and Measurement Results of the proposed SRD filter
4.1 Hardware implementation
4.2 Simulation and Measurement Results

Chapter 5 Conclusion
Reference

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