Metodologia Per la Caratterizzazione di amplificatori a basso rumore per UMTS

In questo lavoro si presenta una metodologia di progettazione elettronica a livello di sistema, affrontando il problema della caratterizzazione dello spazio di progetto dell' amplificatore a basso rumore costituente il primo stadio di un front end a conversione diretta per UMTS realizzato in tecnologia CMOS con lunghezza di canale .18u. La metodologia è sviluppata al fine di valutare in modo quantititativo le specifiche ottime di sistema per il front-end stesso e si basa sul concetto di Piattaforma Analogica, che prevede la costruzione di un modello di prestazioni per il blocco analogico basato su campionamento statistico di indici di prestazioni del blocco stesso, misurati tramite simulazione di dimensionamenti dei componenti attivi e passivi soddisfacenti un set di equazioni specifico della topologia circuitale. Gli indici di prestazioni vengono successivamente ulizzati per parametrizzare modelli comportamentali utilizzati nelle fasi di ottimizzazione a livello di sistema. Modelli comportamentali atti a rappresentare i sistemi RF sono stati pertanto studiati per ottimizzare la scelta delle metriche di prestazioni. L'ottimizzazione dei set di equazioni atti a selezionare le configurazione di interesse per il campionamento ha al tempo stesso richiesto l'approfondimento dei modelli di dispositivi attivi validi in tutte le regioni di funzionamento, e lo studio dettagliato della progettazione degli amplificatori a basso rumore basati su degenerazione induttiva. Inoltre, il problema della modellizzazione a livello di sistema degli effetti della comunicazione tra LNA e Mixer è stato affrontato proponendo e analizzando diverse soluzioni. Il lavoro ha permesso di condurre un'ottimizzazione del front-end UMTS, giungendo a specifiche ottime a livello di sistema per l'amplificatore stesso

Direct tunneling through high-κ\kappa amorphous HfO2_2: effects of chemical modification

We report first principles modeling of quantum tunneling through amorphous HfO$_2$ dielectric layer of metal-oxide-semiconductor (MOS) nanostructures in the form of n-Si/HfO$_2$/Al. In particular we predict that chemically modifying the amorphous HfO$_2$ barrier by doping N and Al atoms in the middle region - far from the two interfaces of the MOS structure, can reduce the gate-to-channel tunnel leakage by more than one order of magnitude. Several other types of modification are found to enhance tunneling or induce substantial band bending in the Si, both are not desired from leakage point of view. By analyzing transmission coefficients and projected density of states, the microscopic physics of electron traversing the tunnel barrier with or without impurity atoms in the high-$\kappa$ dielectric is revealed.Comment: 5 pages, 5 figure

A critical evaluation of direct electrical protein detection methods

During the last decennia many protein-related electrical phenomena have been studied and applied in a variety of measuring systems, from simple metal electrodes with adsorbed proteins to sophisticated systems with lipid bilayers. Many of the investigations concern the monitoring of immuno reactions. The basis underlying electrical effects of the observed phenomena are the protein modulated dielectric constant, conductivity, electrical potential, ion permeability and ion mobility. In this paper special attention is paid to the capacitive measurements with EIS systems as well as impedance and potential measurements with FET devices. The Donnan theory is treated and applied to the static ImmunoFET operation, explaining the relatively small effects which have been reported. Finally, an alternative approach is described in which the ImmunoFET is applied in a dynamic way, to circumvent the drawbacks of the static measurements

Diffusive Transport in Quasi-2D and Quasi-1D Electron Systems

Quantum-confined semiconductor structures are the cornerstone of modern-day electronics. Spatial confinement in these structures leads to formation of discrete low-dimensional subbands. At room temperature, carriers transfer among different states due to efficient scattering with phonons, charged impurities, surface roughness and other electrons, so transport is scattering-limited (diffusive) and well described by the Boltzmann transport equation. In this review, we present the theoretical framework used for the description and simulation of diffusive electron transport in quasi-two-dimensional and quasi-one-dimensional semiconductor structures. Transport in silicon MOSFETs and nanowires is presented in detail.Comment: Review article, to appear in Journal of Computational and Theoretical Nanoscienc

Modelling of field-effect transistors based on 2D materials targeting high-frequency applications

New technologies are necessary for the unprecedented expansion of connectivity and communications in the modern technological society. The specific needs of wireless communication systems in 5G and beyond, as well as devices for the future deployment of Internet of Things has caused that the International Technology Roadmap for Semiconductors, which is the strategic planning document of the semiconductor industry, considered since 2011, graphene and related materials (GRMs) as promising candidates for the future of electronics. Graphene, a one-atom-thick of carbon, is a promising material for high-frequency applications due to its intrinsic superior carrier mobility and very high saturation velocity. These exceptional carrier transport properties suggest that GRM-based field-effect transistors could potentially outperform other technologies. This thesis presents a body of work on the modelling, performance prediction and simulation of GRM-based field-effect transistors and circuits. The main goal of this work is to provide models and tools to ease the following issues: (i) gaining technological control of single layer and bilayer graphene devices and, more generally, devices based on 2D materials, (ii) assessment of radio-frequency (RF) performance and microwave stability, (iii) benchmarking against other existing technologies, (iv) providing guidance for device and circuit design, (v) simulation of circuits formed by GRM-based transistors.Comment: Thesis, 164 pages, http://hdl.handle.net/10803/40531

Switched Capacitor Voltage Converter

This project supports IoT development by reducing the power con- sumption and physical footprint of voltage converters. Our switched- capacitor IC design steps down an input of 1:0 - 1:4 V to 0:6 V for a decade of load current from 5 - 50A

First Order Quasi Static Mosfet Channel Capacitance Model

Conventional MOS models for circuit simulation assume that the channel capacitances do not contribute to net power dissipation. Numerical integration of channel currents and instantaneous terminal voltages however shows the existence of first order dissipating terms. Given that the accuracy of the simulation depends on the physical representation of the device, it is very important that we have a reliable mathematical model that is able to represent the device behavior. Designers need these accurate models for circuit development.To overcome the limitation of conventional charge based models, a self-consistent, first order, quasi-static, power dissipation model has been developed that is able to Predict the exact solution to first order 1-D channel equations for MOSFETs without a channel charge partition approximation provided that the charge has a linear dependence on the channel potential. Validate the terminal currents as being the same as Ward's channel charge partition approximation. Validate that Ward's partition scheme is correct as long as the charge has a linear dependence on the channel potential. Derive the first order channel charge (qc1 ) and current (ic1) as a function of position (x) inside the channel. Derive the first order power dissipation and conserved components. Estimate energy function. Separate the terminal current into conserved and dissipative components. Identify the inconsistencies in the BSIM power model.In conclusion, there is a need to extend this work to include channel charge with a non-linear voltage dependence that does not generate extra power dissipation in the channel that has no physical basis.School of Electrical & Computer Engineerin