الفهرس 
Motivation
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Abstract
Faculty of Engineering Ain Shams University
Electronics and Communication Engineering
Department
Thesis title: ”Interface Circuits Design for piezoresistive Sensors”
Submitted by: Amr Walid Saad Eldain Hassan
Degree: master of Science in Electrical Engineering
Abstract
In the recent years, there has been a growing demand on high
resolution pressure sensors for new applications such as mobile
altimeter, air speed measurements, control systems, medical instruments and accuracy enhancement of the GPS receivers. Many
of these applications are hand-held or battery operated, therefore
the power dissipation of the pressure sensors remains as a main
concern. In piezo-resistive sensors, the pressure to be measured
changes the resistance value of piezo-resistive element. Typically,
piezo-resistive sensors are realized in one of two configurations,
either as a single resistor with current excitation, or in the form of Wheatstone bridge. Although a single resistor configuration can
potentially achieve high signal-to-noise ratio (SNR), the Wheatstone bridge is the most widely used readout configuration, due
to its implementation simplicity and its immunity to common
mode noise and interference from supply and environmental disturbance such as temperature, which in turn relax the interface
circuit design.
Compared to capacitive pressure sensors, piezo-resistive pressure sensors consume dc current in the sensor itself, making resistive sensors less attractive for low-power applications. The objective of this work is to extend the applications of piezo-resistive
sensors to the low power domain. The proposed interface circuit is different than conventional interface circuits by periodically switch the resistive bridge to save power. To reduce the
interface circuit power even further, the turn ON time of different system blocks is optimized. The proposed interface is composed of a sample-and-hold circuit, a front-end-amplifier and a
∆Σ analog-to-digital-converter. The proposed interface is implemented in 0.13µm standard CMOS technology with 1.2V supply
voltage. The interface circuit achieves a high resolution of 13.82
bits with 221.8µW as a total power consumption, including the
bridge power. Hence, a very low figure-of-merit of 5.076 pJ/Conversion is attained.
Keywords: Pressure sensor, low power interface circuit, low
power Wheatstone bridge, resistive pressure sensor, delta-sigma
(∆Σ) modulator, incremental A/D converter.