This dissertation is aimed at the development of a current mode instrumentation amplifier (CMIA) with a high common mode input range. This characteristic is obtained due to the rail-to-rail operational amplifiers (opamps). These opamps are built with rail-to-rail differential amplifiers as input stages, and with cascode-based output stages, which are able to copy its current by adding identical branches and connecting their gates without the voltage degradation as the known CMIA topologies. The main contribution of this work is the development of a rail-to-rail current mode instrumentation amplifier, analyzing the pros and cons of this topology. The functionality of the proposed topology is shown through measured results of a manufactured integrated circuit. This first prototype, although it was operated in a large input common mode range, presented insufficient values of CMRR (Common Mode Rejection Ratio) and VOS (Offset voltage). These two characteristics were studied and modeled, the instrumentation amplifier was re-designed, and simulated results demonstrate important improvements. / Esta dissertação tem como objetivo o desenvolvimento de um amplificador de instrumentação em modo corrente com uma ampla faixa de entrada em modo comum. Esta característica é obtida graças ao emprego de estágios de amplificação rail-to-rail na entrada e a geração do sinal de saída através do espelhamento da corrente diretamente dos gates dos transistores do estágio ao invés da alternativa clássica, onde espelhos são ligados em série e degradam a excursão do sinal de saída. Com esta proposta, é possível a implementação de ampops com entrada e saída rail-to-rail. A principal contribuição deste trabalho é analisar as vantagens e desvantagens da utilização destas soluções na implementação de um amplificador de instrumentação com entrada rail-to-rail. A funcionalidade da topologia proposta é demonstrada através dos resultados medidos de um circuito integrado fabricado. Este primeiro protótipo, apesar do bom funcionamento em toda a faixa de entrada em modo comum, apresentou valores insatisfatórios de CMRR (Common Mode Rejection Ratio) e de VOS (Tensão de offset), o que levou a um aprofundamento no estudo e modelagem destas características. A partir disto, o circuito foi re-projetado e os resultados de simulação demonstram melhorias bastante significativas em suas características.

Cette thèse s’inscrit dans le domaine de la modélisation des circuits analogiques et mixtes.Le travail part d’une problématique industrielle concernant les circuits électroniques utilisés dansles systèmes de forage pétrolier pour des besoins d’instrumentation et mesures. Ce travail de recherche concerne les circuits du front-end analogique que nous trouvons dans cette application industrielle. Nous examinons et nous essayons de trouver des modèles pour décrire l’effet des hautes températures sur les circuits électroniques dans un forage pétrolier. Ces circuits font partie des circuits industriels conventionnels. Ils ont généralement une température maximale de fonctionnement qui ne dépasse pas 125°C. Même si la température modifie le comportement de ces circuits, il existe des techniques d’adaptation qui permettent de compenser l’effet de la température sur ces circuits. Cependant, pour bien réussir la phase de la conception, il faut d’abord bien caractériser le comportement des différents circuits industriels utilisés en haute température. Il faut également trouver des modèles exacts qui décrivent le comportement de ces circuits en haute température. Or nous savons que la majorité des circuits industriels analogiques et mixtes sont décrits par des modèles de type SPICE. Par un choix de l’entreprise Schlumberger, notre partenaire industriel qui a financé ce travail, nous nous sommes intéressés dans notre étude à un composantspécifique présent dans la majorité des circuits analogiques et mixtes d’instrumentation :l’amplificateur opérationnel (l’AOP).Le travail commence par une étude des spécifications du circuit ainsi que le modèle SPICE.Une étude de la structure de ce modèle et sa simulation ont montré la non-précision du modèle audelàde 125°C. L’étude de validité du modèle a concerné le paramètre de la tension de décalage etle paramètre taux de rejection du mode commun. Nous avons interprété la différence des résultatsentre les mesures et la simulation de la tension de décalage. Nous avons constaté la limitation quereprésente l’approche structurelle par modélisation SPICE. Pour cette raison, nous avonssélectionné l’approche de modélisation comportementale pour les différents avantages qu’elleprésente. Ces avantages répondent à nos besoins et conviennent les mesures qui ont été effectuées.Nous avons sélectionné le langage VHDL-AMS et l’environnement Cadence ADVanceMS. Pourdéveloppé les modèles, nous avons alors énuméré les différents paramètres de performance d’unAOP. Nous avons validé la représentation de chaque paramètre par un circuit de test approprié.Dans un deuxième temps, nous avons approximé la variation de ces paramètres en température pardes équations polynomiales et exponentielles pour développer le modèle précis en HT. Le modèlea été validé par un circuit de test similaire au circuit expérimental. De bons résultats ont ététrouvés. L’erreur moyenne entre simulation VHDL-AMS et mesures n’a pas dépassé 3,11%. Dansle denier chapitre, nous avons simulé des circuits d’une chaine d’instrumentation. Nous avonssimulé l’effet de la température sur un capteur piézo-résistif (pont de Wheatstone). Trois architectures d’un amplificateur d’instrumentation ont été également modélisées e en se basant surle modèle VHD-AMS de l’AOP. / This work is dealing with the modelling of analogue and mixed signal circuits. Moreprecisely, we focus on modelling the circuits of an analogue front-end which is used in down-holedrilling industry for instrumentation and measurement purposes. This research had as a goal tomodel the temperature increasing effect in the behaviour of each circuit of the considered frontend.The studied circuits belong to the family of “conventional” circuits. Most of these circuitsoperate in a temperature which does not exceed 125°C. Even if the behaviour of the circuit changesdue to an increasing of the temperature, there are some well-know techniques that enable thecompensation of such effects. However, in order to obtain a precise simulation in the design phase,it is very important to have accurate models that describe the temperature increasing effect. Asmost of the commercial circuits models are written in SPICE, it is necessary first to review theaccuracy of SPICE models in high temperature (HT). This work focus on a specific circuit: theoperational amplifier (opamp). This device is present in many instrumentation circuits. Obtainingan accurate op-amp model in HT will help us develop accurate models of these circuits byconsidering their architectural description which is based on the opamp model.The work starts with the study of the structure of the SPICE model of the considered opamp.This study enables us to confirm the non-validity of the SPICE model in HT. The validity studyconsists in comparing the SPCE simulation results of two parameters (the voltage offset and thecommon mode rejection ratio) to measurement results. Moreover, we present an interpretation tothe difference that was observed in this comparison. After comparing different modellingapproaches, we select the behavioural modelling one. The VHDL-AMS was used to develop thenew precise opamp model in HT. The simulation is performance in Cadence/ADVanceMSenvironment. The representation of each opamp parameter is validated by a specific circuit. Thismodel is developed in two steps. In the first step, we develop an opamp model in which there is noconsideration of the temperature effect. In the second step, dependence of each parameter to thetemperature is described by a polynomial or exponential function. This function is the result of thefitting process of the measurement results. These equations are inserted in the VHDL-AMS model.All parameters are again validated in each temperature. The test-circuit is the same circuit used inthe experimental test of the opamp parameters. The average error between measurement andsimulation does not exceed 3.11%. In the last chapter, we simulate some circuits of the theanalogue front-end of an acquisition system. We simulate for example the effect of the temperatureeffect on the accuracy of a Wheatstone bridge. Three architecture of an instrumentation amplifierwere also modelled and simulated in different temperature of [20°C, 220°C] in the basis of thedeveloped opamp model.

The implementation of portable electroencephalography (EEG) systems has been known to be complex. During ambulation, the integrity of recorded EEG signals is often impaired by motion artifacts and the time and effort required to set up the system is excessive. The use of single-channel EEG systems with dry, active electrodes (AEs) for signal acquisition is a topic of current interest. AEs are electrodes which have integrated bioamplifier circuitry and are known to be less susceptible to motion artifacts and environmental interference. In this report, the design of an AE preamplifier for the purpose of improving single-channel EEG recordings is presented. Initially, a thorough literature review was performed, exploring the available knowledge and state-of-the-art technology. Thereafter, the design specifications were set and the appropriate topology and circuit design techniques were selected to maximize the amplifier’s performance. Ultimately, three different preamplifier topologies were designed and their performance compared with one another as well as with established medical device standards and state-of-the-art AEs. The results of one preamplifier showed comparable performance with state-of-the-art AEs. Therefore, this topology was selected for a deep analysis and physical layout design. The layout of the selected preamplifier was designed and its parasitics extracted. The post layout performance of the design proved to be comparable to the schematic level performance, with a CMRR of 153dB, IRNV of 0.89µVRMS and an electrode offset tolerance of 450mV. The preamplifier design presented in this report has proven to be comparable with state-of-the-art AE preamplifiers and demonstrates potential for the advancement of AE performance in single-channel EEG systems. / Implementeringen av bärbara elektroencefalografisystem (EEG) har varit känd för att vara komplex. Vid rörelse påverkas ofta reliabiliteten av de inspelade EEGsignalerna av rörelseartefakter samt av att tiden och det arbete som krävs för att ställa in systemet blir överdrivet lång. Användandet av singelkanals EEG-system, med torra aktiva elektroder (AE) under inspelningen, är ett aktuellt ämne. En AE är en elektrod som har en integrerad bioförstärkarkrets och är känd för att vara både mindre mottaglig för rörelseartefakter och för störning från omgivningen. I denna rapport presenteras utformningen av en AE-förförstärkare för singelkanals EEGinspelningar. Inledningsvis utfördes en grundlig litteraturöversikt där den rådande kunskapen och toppmoderna tekniken undersöktes. Därefter bestämdes designspecifikationerna, lämpliga topologier samt kretsdesigntekniker, för att maximera förstärkarens prestanda. Slutligen konstruerades tre olika förstärkares topologier och deras prestanda jämfördes med varandra liksom med etablerade medicin tekniska standarder och toppmoderna AE. Resultaten av en förförstärkare visade sig ha jämförbar prestanda med toppmoderna AE. Därför valdes denna topologi ut för en djupanalys och för fysisk layoutkonstruktion. Layouten för den valda förförstärkaren utformades och dess parasiter extraherades. Utformningen av postlayouten visade sig vara jämförbar med prestanda på en schematisk nivå, med en CMRR på 153dB, IRNV på 0.89µVRMS och en elektrodoffsettolerans på 450mV. Förförstärkarens design som presenteras i denna rapport har visat sig vara jämförbar med toppmoderna AE-förförstärkare och visar potential till framsteg för AEprestanda i singelkanals EEG-system

Master’s thesis deals with design of laboratory supply with precise voltage and current measuring. At the beginning it presents properties, advantages and disadvantages of linear and switching supplies, based on these facts it chooses a linear type of regulator. The design continues with detailed description of power and control analog and digital circuits. The thesis includes description of taking control over the supply from the front panel or through computer. The last part is devoted to measurement results and to presentation of some static and dynamic parameters of the designed supply.