Heidelberg, Univ., Diplomarb., 1997.

Heidelberg, Univ., Diss., 2000.

Zugl.: Freiburg (Breisgau), Univ., Diss., 2007

Universiẗat, Diss., 2003--Heidelberg.

University, Diss., 2002--Tübingen.

University, Diss., 2005--Heidelberg.

abstract: This thesis presents a gas sensor readout IC for amperometric and conductometric electrochemical sensors. The Analog Front-End (AFE) readout circuit enables tracking long term exposure to hazardous gas fumes in diesel and gasoline equipments, which may be correlated to diseases. Thus, the detection and discrimination of gases using microelectronic gas sensor system is required. This thesis describes the research, development, implementation and test of a small and portable based prototype platform for chemical gas sensors to enable a low-power and low noise gas detection system. The AFE reads out the outputs of eight conductometric sensor array and eight amperometric sensor arrays. The IC consists of a low noise potentiostat, and associated 9bit current-steering DAC for sensor stimulus, followed by the first order nested chopped £U£G ADC. The conductometric sensor uses a current driven approach for extracting conductance of the sensor depending on gas concentration. The amperometric sensor uses a potentiostat to apply constant voltage to the sensors and an I/V converter to measure current out of the sensor. The core area for the AFE is 2.65x0.95 mm2. The proposed system achieves 91 dB SNR at 1.32 mW quiescent power consumption per channel. With digital offset storage and nested chopping, the readout chain achieves 500 fÝV input referred offset. / Dissertation/Thesis / Ph.D. Electrical Engineering 2011

abstract: The market for high speed camera chips, or image sensors, has experienced rapid growth over the past decades owing to its broad application space in security, biomedical equipment, and mobile devices. CMOS (complementary metal-oxide-semiconductor) technology has significantly improved the performance of the high speed camera chip by enabling the monolithic integration of pixel circuits and on-chip analog-to-digital conversion. However, for low light intensity applications, many CMOS image sensors have a sub-optimum dynamic range, particularly in high speed operation. Thus the requirements for a sensor to have a high frame rate and high fill factor is attracting more attention. Another drawback for the high speed camera chip is its high power demands due to its high operating frequency. Therefore, a CMOS image sensor with high frame rate, high fill factor, high voltage range and low power is difficult to realize. This thesis presents the design of pixel circuit, the pixel array and column readout chain for a high speed camera chip. An integrated PN (positive-negative) junction photodiode and an accompanying ten transistor pixel circuit are implemented using a 0.18 µm CMOS technology. Multiple methods are applied to minimize the subthreshold currents, which is critical for low light detection. A layout sharing technique is used to increase the fill factor to 64.63%. Four programmable gain amplifiers (PGAs) and 10-bit pipeline analog-to-digital converters (ADCs) are added to complete on-chip analog to digital conversion. The simulation results of extracted circuit indicate ENOB (effective number of bits) is greater than 8 bits with FoM (figures of merit) =0.789. The minimum detectable voltage level is determined to be 470μV based on noise analysis. The total power consumption of PGA and ADC is 8.2mW for each conversion. The whole camera chip reaches 10508 frames per second (fps) at full resolution with 3.1mm x 3.4mm area. / Dissertation/Thesis / Masters Thesis Electrical Engineering 2017

Cette thèse présente la conception et la mise en œuvre d'un imageur CMOS pour être utilisé dans biocapteurs intégrés basés sur Résonance Plasmonique de Surface (SPR). Tout d'abord, les conditions optimales pour la résonance plasmon dans une interface compatible CMOS / post-CMOS sont obtenus par modélisation avec COMSOL. Deuxièmement, un imageur CMOS de Colonne Actif (CMOS-ACS) du 32x32 pixels est mis en œuvre sur une technologie CMOS 0,35 um. Dans une interface d'or-eau avec une excitation de prisme, on constate que pour les prismes avec des indices de réfraction de 1,55 et 1,46, le couplage optimal avec le plasmon est obtenu pour des films d'or d'une épaisseur de 50 et 45 nm, respectivement. Dans ces conditions, environ 99,19% et 99,99% de l'énergie de la lumière incidente est transférée à le surface plasmon pour les deux prismes respectivement, à condition que la lumière incidente, avec une longueur d'onde de 633 nm, arrive avec un angle d'incidence de 68,45° et 79,05° respectivement. Il est également obtenu qu'un changement de RIU 10-4 de l'indice de réfraction du milieu diélectrique, produit un changement de 0,01 ° dans l'angle de résonance de plasmons qui, dans un schéma de modulation d'intensité de lumière produit une variation de 0,08% dans la lumière réfléchie au photodétecteur. En ce qui concerne le imageur CMOS, une photodiode n-well/p-substrate est choisi comme l'élément de photodétection, en raison de sa faible capacité de jonction, ce qui conduit à un rendement élevé et le gain de conversion élevé comparativement à une photodiode n-diff/p-substrate. Des simulations sur ordinateur avec Cadence et Silvaco produit une capacité de jonction de 31 FF et 135 fF respectivement. Le pixel de l'imageur est basé sur une configuration à trois transistors (3T) et présente un facteur de remplissage de 61%. Le circuit de lecture utilise une technique de capteur de colonne actif (ACS) pour réduire le bruit à motif fixe (Fixed Pattern Noise ou FPN en anglais) liée au le Capteur à Pixels Actif (APS) traditionnelle. En outre, Non-Corrélés Echantillonnage Double (Non-Correlated Double Sampling ou NCDS en anglais) et Delta double échantillonnage (DDS) sont utilisés comme techniques de réduction du bruit. Un montage optique expérimental est utilisé pour caractériser les performances de l'imageur, et nous avons obtenu un gain en conversion de 7,3 uV/e-, une capacité de jonction de la photodiode de 22 fF, un bruit de lecture de 324,5 uV, ce qui équivaut à 45 électrons, et une gamme dynamique de 50,5 dB. Les avantages de l'ACS et NCDS-DDS sont observées dans le niveau faible de FPN du pixel et de la colonne, avec une valeur de 0,09% et 0,06% respectivement. Le travail présenté dans cette thèse est une première étape vers l'objectif de développer une plateforme entièrement intégrée SPR pour biocapteurs, incorporant source de lumière, l'interface SPR, canal microfluidique, les éléments d'optique et imageur CMOS. / This dissertation presents the design and implementation of a CMOS imager for use in integrated biosensors based on Surface Plasmon Resonance. First, the optimal conditions for plasmon resonance in a CMOS/Post-CMOS compatible interface are obtained by COMSOL modelling. Second, a 32x32-pixel CMOS-Active Column Sensor (CMOS-ACS) is implemented on 0.35 um CMOS technology. In a gold-water interface with prism excitation, it is found that for prisms showing refractive indexes of 1.55 and 1.46, optimal plasmon coupling is obtained for gold films with thicknesses of 50 and 45 nm respectively. Under these conditions, approximately 99.19% and 99.99% of the incident light's energy is transferred to the surface plasmon for both prism respectively, provided that the incident light, with a wavelength of 633 nm, arrives with incidence angles of 68.45° and 79.05° respectively. It is also obtained that a change of 10-4 RIU in the refractive index of the dielectric medium, produces a change of 0.01° in the plasmon resonance angle, which under a light intensity modulation scheme produces a change of 0.08% in the reflected light's energy reaching the photodetector. Concerning the CMOS imager, a n-well/p-substrate photodiode is selected as the photosensing element, due to its low junction capacitance, which results in high efficiency and high conversion gain compared to the n-diff/p-substrate photodiode. Computer simulations with Cadence and Silvaco produced a junction capacitance of 31 fF and 135 fF respectively. The imager's pixel is based on a three-transistor (3T) configuration and shows a fill factor of 61%. The readout circuitry employs an Active Column Sensor (ACS) technique to reduce the Fixed Pattern Noise (FPN) associated with traditional Active Pixel Sensors (APS). Additionally, Non-Correlated Double Sampling (NCDS) and Delta Double Sampling (DDS) are used as noise reduction techniques. An experimental optical setup is used to characterize the performance of the imager, obtaining a conversion gain of 7.3 uV/e-, a photodiode junction capacitance of 21.9 fF, a read noise of 324.5 uV, equivalent to ~45 e- and a dynamic range of 50.5 dB. The benefits of ACS and NCDS-DDS are observed in the low pixel and column FPN of 0.09% and 0.06% respectively. The work presented in this thesis is a first step towards the goal of developing a fully integrated SPR-biosensing platform incorporating light source, SPR interface, microfluidic channel, optical elements and CMOS imager.

abstract: Analysing and measuring of biological or biochemical processes are of utmost importance for medical, biological and biotechnological applications. Point of care diagnostic system, composing of biosensors, have promising applications for providing cheap, accurate and portable diagnosis. Owing to these expanding medical applications and advances made by semiconductor industry biosensors have seen a tremendous growth in the past few decades. Also emergence of microfluidics and non-invasive biosensing applications are other marker propellers. Analyzing biological signals using transducers is difficult due to the challenges in interfacing an electronic system to the biological environment. Detection limit, detection time, dynamic range, specificity to the analyte, sensitivity and reliability of these devices are some of the challenges in developing and integrating these devices. Significant amount of research in the field of biosensors has been focused on improving the design, fabrication process and their integration with microfluidics to address these challenges. This work presents new techniques, design and systems to improve the interface between the electronic system and the biological environment. This dissertation uses CMOS circuit design to improve the reliability of these devices. Also this work addresses the challenges in designing the electronic system used for processing the output of the transducer, which converts biological signal into electronic signal. / Dissertation/Thesis / M.S. Electrical Engineering 2014