خط مشی دسترسیدرباره ماپشتیبانی آنلاین
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Document Type:Latin Dissertation
Language of Document:English
Record Number:52742
Doc. No:TL22696
Call number:‭NR36179‬
Main Entry:Mohammad Maymandi-Nejad
Title & Author:Low-voltage/low power analog circuits for bio-implantable applicationsMohammad Maymandi-Nejad
College:University of Waterloo (Canada)
Date:2005
Degree:Ph.D.
student score:2005
Page No:163
Abstract:CMOS technology is the backbone of integrated circuit industry. This is primarily due to cost effectiveness and low power consumption of CMOS circuits. During the last few decades CMOS technology has scaled down aggressively. This has brought new opportunities and challenges. Power consumption and low supply voltage are two of the challenges that circuit designers are facing. Hence, many researchers are trying to find circuit and system techniques which consume less power and are able to operate will lower supply voltages. Meanwhile, device and circuit knowledge and techniques obtained during the past few decades in integrated circuits has encouraged researchers to look for new applications in biomedical domain. Due to the low power feature, CMOS technology is the first choice of circuit designers for bio-implantable circuits where power consumption is the primary design issue. In this research, a wireless telemetered bio-implantable blood pressure system for transgenic mice is implemented, which is the major contribution of this thesis. The designed system has two parts. An implantable device inside the body of a mouse measures the blood pressure and transmits the data outside the body. A receiver at a distance of about 50cm detects the transmitted signal and extracts the pressure data. Due to limited available space in the implantable part, a single miniature battery is the source of energy, and therefore, power consumption is the primary design issue in this application. The voltage of most available miniature batteries changes from 1.6V to 0.9V over time and using such a battery as the power supply of an integrated circuit is challenging. The integrated circuit should be able to operate using a low supply voltage, tolerate about 60% voltage variations, and consume low power at the same time. On the other hand at the receiver side the power consumption is not an issue and the receiver circuit can be implemented using off the shelf components. In this thesis our focus will be on the implant part of the system. The specifications of the designed implant chip exceed that of the state of the art comparable devices. This has become possible by using several novel techniques at the system level as well as circuit level. In order to reduce the power consumption of the implant, not only have we tried to use low power circuit architectures, but also have added a power saving scheme to the IC. Meanwhile, the MEMS pressure sensor used for this application, suffers from several non-idealities; i.e. mismatch, temperature coefficient of sensor resistors (TCR), and temperature coefficient of the gauge factor (TCGF). We have used a Wheatstone bridge configuration with two current sources (instead of two completion resistors) to deal with these non-idealities. In order to compensate the impact of temperature, the temperature coefficient of the two currents (TCI) should be adjusted according to TCR and TCGF. Generation of a current with any desirable TCI is feasible in CMOS technology and we have developed a new technique to generate a constant current with any TCI. The TCI of the current source can be adjusted in field via a digital input vector. Simultaneous data of heart volume and blood pressure can provide more valuable information about the activity and performance of heart. The measurement of the left ventricle volume is also addressed in this thesis, although it is not part of the designed implant. We have proposed a new technique for blood volume measurement using a square wave signal. The proposed method is advantageous in terms of power consumption and silicon area. In many biomedical applications there is a need to convert analog signals to digital data. On the other hand being low power and low voltage is a necessity for bio-implantable applications. We have explored the design issues of low voltage ΔΣ modulators. We have used dynamic threshold MOSFET (DTMOS) technique in the implementation of the modulator to enhance the performance of modulator's blocks. It is shown how this technique can be useful in the design of low voltage analog circuits.
Subject:Applied sciences; Analog circuits; Bioimplants; CMOS; Electrical engineering; 0544:Electrical engineering
Added Entry:University of Waterloo (Canada)