UNIVERSITA’ DEGLI STUDI DI PADOVA
Dipartimento di Ingegneria dell’Informazione
Research topics
1. CHARACTERIZATION OF WIDE BANDGAP GaN-based SEMICONDUCTOR DEVICES
G. Meneghesso, E. Zanoni
Collaborazioni: University of California, Santa Barbara, University of Lille, IEMN, France, University of Virginia, Department of Electrical Engineering, VA, USA, Rensselaer Polytechnic Instit., Troy New York, Istituto LAMEL CNR, Bologna; Selex-SI, Roma (Italy), UMS - Ulm (Germany), PICOGIGA, Paris (France), III-V Labs, Marcoussy, (France), IEMN, Lille (France), Fraunhofer IAF (Germany)
1. CHARACTERIZATION, MODELING AND RELIABILITY OF ADVANCED OPTOELECTRONIC DEVICES: TOWARDS HIGH EFFICIENCY LEDS, LASERS AND SOLAR CELLS
G. Meneghesso, E. Zanoni
Collaborations: OSRAM-OptoSemiconductors (Germany), Panasonic Corporation (Japan), Sensor Electronic Technology Inc. (USA), Tridonic-ATCO (now LEDON-Lighting, Austria), OSRAM Spa (Italy), Centro Ricerche Plastoptica (Italy), University of Cambridge (UK), Univeristy of Parma (Italy), University of Bologna (Italy), University of Cagliari (Italy)
3. DESIGN AND CONTROL OF SWITCH MODE POWER SUPPLIES (SMPS)
S. Buso, L. Corradini, P. Mattavelli, L. Rossetto, G. Spiazzi, P. Tenti
Collaborations: CERN, Ginevra (CH), University of Campinas, UNICAMP (BR), Dept. of Technology and Management of Industrial Systems, University of Padova
Homepage: http://pelgroup.dei.unipd.it/
4. DEVELOPMENT AND RELIABILITY INVESTIGATION OF RADIO FREQUENCY MICRO ELECTRO MECHANICAL SYSTEMS (RF-MEMS)
G. Meneghesso
Collaborations: Fondazione Bruno Kessler Trento (former ITC-IRST), University of Perugia (Italy), University of Torino (Italy), University of Lecce (Italy), Ecole Polytechnique Federale de Lausanne (EPFL), Switzerland, LAAS, Tolosa (F), Selex-SI, Roma, EPFL, Losanna (CH), CSEM, Neuchatel (CH).
5. LOW-POWER INTEGRATED CIRCUITS FOR WIRELESS COMMUNICATION
A. Bevilacqua, A. Gerosa, A. Neviani, D. Vogrig
Collaborations: Università di Pavia, Politecnico di Milano
Homepage: http://icarus.dei.unipd.it
6. RADIOFREQUENCY INTEGRATED CIRCUITS DESIGN FOR BIOMEDICAL RADARS AND IMAGING
A. Bevilacqua, A. Gerosa, A. Neviani, D. Vogrig
Collaborations: Università di Pavia, Università di California, Berkeley
Homepage: http://icarus.dei.unipd.it
7. MICROELECTRONICS FOR HUMAN HEALTH CARE
A. Paccagnella
Collaborations: Azienda ospedaliera di Vicenza reparto di Nefrologia, Azienda ospedaliera di Padova reparto Gastroenterologia, Next Step Engineering s.r.l. (Spin-off Università di Padova), Wetware Concepts s.r.l. (Spin-off Università di Padova), FBK-IRST, INFN Laboratori Nazionali Legnaro.
8. SOFT ERRORS IN ADVANCED ELECTRONIC COMPONENTS
A. Paccagnella
Collaborations: ESA-ESTEC, NASA-JPL, Numonyx, Thales Alenia Space, RFX ITER, ASI, RedCat devices, Rutherford Appleton Laboratories, INFN Laboratori Nazionali Legnaro, The Svedberg Laboratory, Sandia National Labs, and various universities across Italy.
Homepage: http://rreact.dei.unipd.it
9. ORGANICS TECHNOLOGIES: THE KEYSTONE FOR ELECTRONIC, LIGHT, AND ENERGY ANYWHERE
A. Cester, G. Meneghesso
Collaborations: Universal Display Corporation, Bratislava University, University of Rome – Tor Vergata, C.H.O.S.E. – Polo solare regione Lazio, IMEC
Homepage: http://most.dei.unipd.it
10. RENEWABLE ENERGY SOURCES
S. Buso, L. Corradini, P. Mattavelli, L. Rossetto, G. Spiazzi, P. Tenti
Collaborations: National Semiconductors, ST Microelectronics, Selco Engineering, Exergy Fuel Cells.
Homepage: http://pelgroup.dei.unipd.it/
CHARACTERIZATION OF WIDE BANDGAP GaN-based SEMICONDUCTOR DEVICES
G. Meneghesso, E. Zanoni
The wide bandgap semiconductor gallium nitride (GaN) and related materials are highly attractive for high-power and high-temperature applications. Significant results have been obtained in the fabrication of GaN-based microwave power field effect transistors, demonstrating impressive DC and rf characteristics. However, instabilities related to materials and trapping effects limit the reproducibility and the performance of these devices. A decrease of the drain current, ID, during operation and after Hot electron tests has been observed during this research activity.
We have investigated the rf current collapse phenomenon in AlGaN/GaN HEMTs by means of pulsed, transient, and small-signal measurements. Moreover, 2D numerical device simulations have been for the first time adopted to analyze the influence of surface states on the pulsed characteristics of AlGaN/GaN HEMTs. Simulations point out that an additional mechanism exists, capable of explaining the surface-related ID collapse and the correlated dispersion effects. Owing to the negative polarization charge, bands are actually bent upwards at the ungated surface. This makes the occupation of energy levels relatively close to the top of the valence band (EV) susceptible to be modulated by bias changes through hole exchange with the valence band.
Traps have been identified in AlGaN-GaN HEMTs by means of different characterization techniques and the associated physical behavior has been interpreted with the aid of numerical device simulations. It has in particular been shown that, under specific bias conditions, buffer traps can produce the same type of current-mode DLTS (I-DLTS), ICTS, and gm-dispersion signals that are generally attributed to surface traps. Clarifying this fact is crucial for both reliability testing and device optimization, as it can completely hinder a correct identification of degradation mechanisms.
We have also investigate the kink effect in AlGaN/GaN HEMTs. A correlation between kink and threshold voltage shift has been found. Kink is possible due to negative charge build-up, taking place at low VDS values followed by negative charge detrapping or compensation, occurring for high VDS values. Dynamic measurements strongly suggests carrier trapping and detrapping as possible explanation. Photo-stimulated measurements have been also carried out in order to verify whether charge build-up and removal were due to trapping/detrapping mechanisms.
We have also carried out a detailed characterization of long-term aging (by means of both high temperature storage and hot-electron stress) in unpassivated GaN/AlGaN/GaN HEMTs on SiC substrates. We have carefully investigated high-electric-field degradation phenomena of GaN-capped AlGaN-GaN HEMTs by comparing experimental data with numerical device simulations. Simulations indicate that the stress-induced amplification of gate lag effects and the correlated gate-leakage-current reduction can be ascribed to the generation of acceptor traps at the gate-drain surface and/or in the device barrier. The drop in DC drain current observed after stress should rather be attributed to trap accumulation within the GaN buffer region.
CHARACTERIZATION, MODELING AND RELIABILITY OF ADVANCED OPTOELECTRONIC DEVICES: TOWARDS HIGH EFFICIENCY LEDS, LASERS AND SOLAR CELLS
G. Meneghesso, E. Zanoni
Over the last years, gallium nitride has emerged as an excellent material for the realization of optoelectronic devices emitting in the visible (blue, green) and ultraviolet spectral region. Gallium nitride (GaN)-based light-emitting diodes (LEDs) represent almost ideal devices for the realization of the next-generation light sources due to their high efficiencies, long expected lifetime, high robustness to breakdown and electrostatic discharges (ESDs), and low expected cost of ownership, plus the possibility of tailoring the emission wavelength by an accurate control of the compositional properties of the materials. The performance improvements introduced by many research groups worldwide have enabled several applications for visible LEDs, particularly in the fields of solid-state lighting, display backlighting, automotive, and portable systems.
On the other hand, short-wavelength (375-405 nm) laser diodes based on Gallium Nitride will soon find application in many fields including optical data storage (Blu-Ray Discs), biomedical devices and optical devices.
Despite the excellent potential of GaN-based optoelectronic devices, their performance and reliability is still limited by a number of technological issues. The aim of our research activity is to characterize and model the physical mechanisms that limit the performance and the lifetime of advanced LED and laser structures. Furthermore, we work towards the development of advanced illumination devices based on LEDs, with long lifetime, controllable output spectrum and high performance. Our activity is also focused towards the development of applications of LEDs and lasers in the fields of environmental science (e.g water treatment, decontamination) and energy efficiency (e.g. photovoltaics).
A future research line of our group concerns photovoltaics: the optoelectronics laboratory is acquiring also instrumentation for the electrical, optical and spectroscopic characterization of advanced solar cells based on Silicon, thin film and compound semiconductor.
Our group cooperates/has cooperated with many manufacturers of optoelectronic devices worldwide, including OSRAM-OptoSemiconductors (Germany), Panasonic Corporation (Japan), Sensor Electronic Technology Inc. (USA), Tridonic-ATCO (now LEDON-Lighting, Austria), OSRAM Spa (Italy), Centro Ricerche Plastoptica (Italy).
DESIGN AND CONTROL OF SWITCH MODE POWER SUPPLIES (SMPS)
S. Buso, L. Corradini, P. Mattavelli, L. Rossetto, G. Spiazzi, P. Tenti
The presented research activity deals with the analysis and the design of high frequency power supplies for a large variety of applications. The efforts are toward the search for converter topologies and control strategies aimed to increase the performances in terms of overall conversion efficiency, dynamic response to abrupt input voltage or load current changes and volume. The main application fields are:
• high-frequency dc-dc converters for microprocessors and low-voltage electronics circuits for signal processing;
• line-fed high-frequency ac-dc converters for high-brightness LED (solid-state lighting);
• dc-dc converters and inverters for photovoltaic modules and fuel-cells;
• high-frequency dc-ac inverters for fluorescent lamps.
Each application field has its own challenges. For example, the power supplies for microprocessors are characterized by an extremely low output voltage (0.8-3V) and high current (1-100A) and may are requested to operate in a very hard environment. This is the case of the research activity done in collaboration with CERN regarding the study and design of coreless Point of Load (PoL) dc-dc converters operating with a high step-down ratio. These converters are intended to be used in distributed power systems for hostile environments, i.e. characterized by high radiation levels as well as high DC magnetic fields, like the supply systems for particle sensors and related electronics for signal conditioning used in high energy physics experiments at CERN (Super Large Hadron Collider - SLHC).
The replacement of incandescent and compact fluorescent lamps with solid-state lamps requires the development of very compact power supplies able to provide a controlled dc current for the LEDs with a minimum volume occupation and maximum conversion efficiency, and also with a minim impact toward the line grid in terms of injection of undesired current harmonics. The possibility of controlling the light quality in terms of colour temperature by mixing different colours is another interesting aspect that needs a suitable control organization and sensing strategies.
Besides the search for optimal converter topologies for a given application, the research efforts are also dedicated to the analysis and design of suitable control systems able to improve stability and dynamic performances. Besides conventional analog control implementations, also mixed-signal approaches, that exploit the numerous advantages of the digital signal processing, are being investigated, thanks to the continuous decrease of their implementation costs. The partially digital implementation of the control algorithms allows to achieve a much better robustness against parameter and environmental condition variations, it gives the possibility of adapting the control parameters to different operating conditions (autotuning), it allows the implementation of sophisticated start-up procedures as well as power management strategies like the output voltage dynamic control and the management of failure conditions, and it makes easier the communication with a supervisor system.
DEVELOPMENT AND RELIABILITY INVESTIGATION OF RADIO FREQUENCY MICRO ELECTRO MECHANICAL SYSTEMS (RF-MEMS)
G. Meneghesso
Emerging and future autonomous, wireless communications systems require highly reliable electronic components with very low power consumption, and micromechanical switches present a promising technology to meet this demand. MEMS switches are devices that use mechanical movement to achieve a short circuit or an open circuit in the RF transmission line. RF MEMS switches are the specific micromechanical switches that are designed to operate at RF-to-millimeter-wave frequencies (0.1 to 100 GHz). Such RF switches have been demonstrated with low loss, low power consumption, low distortion, and higher off-state isolation as compared to p-i-n diodes or field effect transistors. The high cost of packaging such devices has also limited their commercial acceptance. Moreover, their power handling capability is normally much lower than 1 W, and reliability concerns become more pronounced.
The reliability of MEMS switches is of major concern for long term applications and is currently the subject of an intense research effort. Actually, many MEMS switches have been tested up to 100 billion cycles with no observed mechanical failure around the anchors (the location of maximum strain). For ohmic-contact switches, the main failure mechanisms are due to the increase of the contact resistance or to the bonding of the metal surfaces, whereas for capacitive switches, the main failure mechanism is due to stiction, caused by charge trapping.
In this research work we have carried out an extensive electrical characterization in order to identify the dynamic response of RF-MEMS switches driven in different conditions of bias and actuation time. We have found that an optimum actuation voltage must be chosen as a trade-off between good switch transmission and isolation properties and the need to avoid bouncing phenomena when the actuation voltage has been applied. We have also found that, in order to avoid artifact or inconsistent measurements, standardization in the measurement setup is required, and both the actuated and un-actuated states must be analyzed.
For what concern radiation effects, the sensitivity to 1Mrad Total Ionizing Dose (TID) has been evaluated using a 50KeV, 500rad/s, X-ray source available at INFN-LNL (Legnaro, Italy). Several devices have been tested with different layouts and configurations. The very interesting result is tha the TID induced degradation is very similar to the degradation caused b low voltage cycling, indicating that the radiation could be studied as a new accelerating factor for long term stress. We have seen that the suspensions shape plays a very important role also concerning radiation stresses. The reliability results obtained during cycling and continuous actuation stresses are in fact confirmed also considering X-rays stresses: meanders based devices are typically more prone to stiction phenomena or de-actuation issues than higher-k spring-based suspensions. All the information acquired are currently used to properly define design rules in order to build high-performance and reliable devices.
LOW-POWER INTEGRATED CIRCUITS FOR WIRELESS COMMUNICATION
A. Bevilacqua, A. Gerosa, A. Neviani, D. Vogrig
The availability of ultra low-power transceivers, which can be supplied using micro-battery or harvesting energy from the environment, is a key factor for the realization of several devices, whose importance is increasingly growing, such as wireless sensor networks, body area networks and biomedical implantable micro devices. These systems are making several new applications feasible, such as environmental control, room monitoring to maximize energy efficiency, off-line control of medical data, parameter analysis and local drugs administration by means of implanted micro devices. All these systems need to broadcast their data on a radio link, between internal nodes or towards an external base station. Among all the node activities, radio communication is for sure the most power-hungry, hence the need for more and more efficient transceivers. The main goal of our research activity in this field, is to investigate new architectures and to single out efficient circuit solutions that can be profitably used in short-range transceivers for the afore-mentioned applications. In particular, the ongoing projects deal with: (a) developing an impulse radio ultra-wide band (IR-UWB) transceiver for a 10m link, suitable for wireless sensor networks; (b) investigating an ultra-low power transceiver for an implantable micro sensor for continuous monitoring of physiological parameters.
RADIOFREQUENCY INTEGRATED CIRCUITS DESIGN FOR BIOMEDICAL RADARS AND IMAGING
A. Bevilacqua, A. Gerosa, A. Neviani, D. Vogrig
Exploiting microwaves in order to replace or at least support the use of X rays and magnetic resonance for the diagnosis of some kinds of diseases and, more generally, for biomedical imaging, has been a hot research topic in the last decade. Although several promising results have been achieved (e.g. in the field of early detection of breast cancer), the availability at reasonable cost of microwave-based diagnostic instrumentation heavily depends on the capability of realizing application-specific hardware (i.e. integrated circuits) using the same micro- or nano-technologies developed for consumer electronics. From this point of view, the most challenging blocks for these systems are the analog and radiofrequency front-end required in order to generate the microwaves and to detect and condition the signal reflected by the targets. The main goal of our research activity is to single out and to fabricate integrated prototypes of these critical blocks, using CMOS technologies. In particular, the on-going activities are focused on: (a) radar in the 3-20GHz band suited for a breast cancer early detection system; (b) microwave radar for skin imaging.
MICROELECTRONICS FOR HUMAN HEALTH CARE
A. Paccagnella
During the last decades, the need to develop high-performance and accurate equipments suitable for biological and biomedical applications pushes researchers toward carefully studying the complex laws beneath the interaction between microelectronic solid state and biological environments liquid state.
The effort spent in adapting a well-known solid state electronic know-how to an highly sensitive and erratic sector such that related to the interaction between semiconductors and biological systems, enables the growth of research fields hardly predictable without the availability of devices that allow micrometric, and recently also nanometric, scale analysis
During the past decade, inside the Microelectronics research group of the University of Padova’s Department of Information Engineering has been established a team devote to innovative microelectronic systems development for analysis and manipulation in biological and biomedical fields.
The aim of the group, directed by Prof. Alessandro Paccagnella, is to use the great opportunities offered by microelectronics in order to develop new microsystems (Lab-on-chip) able to both improve biological analysis technique and deepen the knowledge of biological phenomena otherwise difficult to investigate.
In particular the activity is focused on the comprehension, modeling and therefore develop of innovative devices designed for both working in hostile environments, e.g. high humidity, extreme pH and high saline concentrations, and interfacing in active and passive ways with biologic world.
The devices that have been studied and developed during different projects have the target of using electronics both as sensors and as actuators. By using as sensors the microelectronic components introduced in these biomedical-oriented chips, they offer the possibility to quantify in real time both concentrations of analytes, e.g. bacteria, cells, proteins and antigens, and the state variations in biological environment, e.g. pH, temperature and saline. Otherwise, when used as actuators, they allow to induce local changes in the biological system, e.g. drug absorption, chemical reactions inhibition or acceleration and biologic material displacement.
SOFT ERRORS IN ADVANCED ELECTRONIC COMPONENTS
A. Paccagnella
The outer space is populated by a large number of high-energy particles. Every second the sun alone emits a million tons of mass, mainly protons, part of which impinges on the atmosphere after some minutes of travelling. Other particles reach the Earth after wandering for millions of years across the universe. These particles interact with the atmosphere, generating a cascade of thousands of particles. Some of these, mainly neutrons, reach the ground, striking electronic circuits and inducing several kinds of malfunctions. For the most part, no permanent damage is induced, but the generated errors can switch the logical state (bit) of a memory element. If not corrected, these errors are a serious threat to the reliability of electronic computations. Data corruption in a pacemaker or in a car ABS may have dramatic consequences. The situation is even worse with avionics, which must operate reliably at high altitude, where the neutron flux is hundreds of times higher than at sea level.
Until a few years ago, the risk was appreciable only in very harsh environments (e.g. space, high energy physics experiments, medical treatments, and nuclear power plants). Today, in the latest semiconductor technologies the radiation sensitivity has increased to a point where ground-level effects can no longer be neglected for critical applications (automotive, biomedical devices, etc.).
Our research group is focused on understanding the ionizing radiation response of circuits built with the latest technologies (e.g. FinFETs, Charge Trap memories, etc.), to be used in critical applications. This is done both through experiments, exposing electronic devices (MOSFETs, SRAMs, Flash memories, microprocessors, and FPGAs ) to accelerated beams of particles available in large facilities worldwide (Legnaro, Lovanio, Uppsala, Didcot, Vancouver); through simulations (SPICE, TCAD, and radiation transport); and analytical modeling. From these studies, mitigations strategies are elaborated to increase the level of reliability and dependability of critical applications.
ORGANICS TECHNOLOGIES: THE KEYSTONE FOR ELECTRONIC, LIGHT, AND ENERGY ANYWHERE
A. Cester, G. Meneghesso
Organic electronics has recently emerged as a low cost alternative to conventional electronics. The low cost of materials and of the fabrication processes mean that large devices can be produced economically. Organic electronics can be developed on flexible, large area substrates with arbitrary shape, both in vacuum and in air, at ambient temperature and pressure.
In particular, by organic electronics it is possible to realize both active devices (Organic Thin-Film Transistors, OTFTs) and optoelectronic devices (Organic Light-Emitting Diodes, OLEDs, and Organic Solar Cells, OSCs).
Organics open to new applications impossible to achieve using silicon: flexible electronics, smart textiles, transparent electronics, printable electronics, …
There are many applications where the performances of organic electronics are already sufficient, including large-area sensors, displays, and circuit applications (for OTFTs), portable devices, car dashboards and televisions (for OLEDs), and calculators, thermometers, clocks and price tags (for OSCs). However, the performance and the lifetime of organic electronic devices are still below the specifications imposed by the market.
Our research efforts are devoted to investigate the most important factors that limit the performance and the reliability of state-of-the-art organic semiconductor devices for electronics and optoelectronics applications. Our research interests range over a wide variety of subjects:
- The characterization of the properties and stability of organic materials and devices.
- The investigation of devices reliability dependence on stress parameters (e.g., voltage, current, or temperature) and the extrapolation of the device degradation laws.
- The study of the impact of the structural parameters (e.g., layer composition and thickness, contact materials, …) on the reliability of the devices.
- The determination of the factors that limit the reliability of organic devices.
RENEWABLE ENERGY SOURCES
S. Buso, L. Corradini, P. Mattavelli, L. Rossetto, G. Spiazzi, P. Tenti
The purpose of the research program is to study devices, circuits and the related control techniques for the exploitation of renewable energy sources, with particular emphasis on the photovoltaic and hydrogen fuel cell technologies. The energy flowing from these sources needs to be properly converted before it is delivered to the typical users, the most important being the utility grid itself. The conversion processes can be effectively performed by switching power converters, whose ideal, target characteristics are: high conversion efficiency, minimal generation of electromagnetic noise, high reliability and maximum power density (minimum volume occupation for a given amount of processed power). The study of such switching converters involves both the development of novel topologies and the identification of suitable control strategies, allowing the achievement of the expected performance.
Pubblications in 2011
1) SOLDA S, CARUSO M, A. BEVILACQUA, GEROSA A, VOGRIG D, NEVIANI A (2011). A 5 Mb/s UWB-IR Transceiver Front-End for Wireless Sensor Networks in 0.13um CMOS. IEEE JOURNAL OF SOLID-STATE CIRCUITS, vol. 46, p. 1636-1647, ISSN: 0018-9200, doi: 10.1109/JSSC.2011.2144070
2) Fabio Alessio Marino, and Gaudenzio Meneghesso, “WJM Multifunctional Field-Effect Transistor for High-Density Integrated Circuits”, IEEE Electron Device Letters, vol. 32, No. 3, pp. 264-266, 2011 DOI 10.1109/LED.2010.2099097
3) N. Wrachien, A. Cester, Y. Q. Wu, P. D. Ye, E. Zanoni, and G. Meneghesso, “Effects of Positive and Negative Stresses on III–V MOSFETs With Al2O3 Gate Dielectric”, IEEE Electron Device Letters, vol. 32, No. 4, pp. 488-490, 2011 DOI 10.1109/LED.2011.2106107
4) A.Tazzoli and G. Meneghesso, “Acceleration of Microwelding on Ohmic RF-MEMS Switches”, IEEE Journal of MicroElectroMechanical Systems, vol. 20, No. 3, pp. 552-554, 2011 DOI 10.1109/JMEMS.2011.2140360 (IUNET, ENIAC-END)
5) M. Meneghini, N. Ronchi, A. Stocco, G. Meneghesso, U. K. Mishra, Yi Pei, E. Zanoni, “Investigation of trapping and hot-electron effects in GaN HEMTs by means of a combined electro-optical method”, IEEE Transaction on Electron Devices, Vol. 58, No. 9, pp. 2296-3003, 2011. doi: 10.1109/TED.2011.2160547
6) M. Meneghini, C. de Santi, N. Trivellin, K. Orita, S. Takigawa, T. Tanaka, D. Ueda, G. Meneghesso, and E. Zanoni, “Investigation of the deep level involved in InGaN laser degradation by Deep Level Transient Spectroscopy”, Applied Physics Letters vol. 99, 093506, 2011. doi:10.1063/1.3626280
7) N. Wrachien, A. Cester, D. Bari, J. Kovac, J. Jakabovic, D. Donoval, G. Meneghesso, “Near-UV Irradiation Effects on Pentacene-Based Organic Thin Film Transistors”, IEEE Transaction on Nuclear Science, Vol. 58, No. 6, pp. 2911-2917, 2011. doi: 10.1109/TNS.2011.2170432
8) Orlandi S., Allongue B., Blanchot G., S. BUSO, Faccio F., Fuentes Rojas C., Kayal M., Michelis S., Spiazzi G. (2011). Optimization of shielded PCB air-core toroids for high efficiency dc-dc converters. IEEE TRANSACTIONS ON POWER ELECTRONICS, vol. 26, p. 1837-1846, ISSN: 0885-8993, doi: 10.1109/TPEL.2010.2090902
9) G. SPIAZZI, P. Mattavelli, A. Costabeber (2011). High Step-Up Ratio Flyback Converter With Active Clamp and Voltage Multiplier. IEEE TRANSACTIONS ON POWER ELECTRONICS, vol. 26, p. 3205-3214, ISSN: 0885-8993, doi: 10.1109/TPEL.2011.2134871
10) S. MOON, L. CORRADINI, D. MAKSIMOVIC (2011). Autotuning of Digitally Controlled Boost Power Factor Correction Rectifiers. IEEE TRANSACTIONS ON POWER ELECTRONICS, vol. 26, p. 3006-3018, ISSN: 0885-8993, doi: 10.1109/TPEL.2011.2125802
11) L. CORRADINI, A. BJELETIC, R. ZANE, D. MAKSIMOVIC (2011). Fully Digital Hysteretic Modulator for DC-DC Switching Converters. IEEE TRANSACTIONS ON POWER ELECTRONICS, vol. 26, p. 2969-2979, ISSN: 0885-8993, doi: 10.1109/TPEL.2010.2055244
12) P. TENTI, H.K. MORALES PAREDES, P. MATTAVELLI (2011). Conservative Power Theory, a Framework to Approach Control and Accountability Issues in Smart Microgrids . IEEE TRANSACTIONS ON POWER ELECTRONICS, vol. 60, p. 664-673, ISSN: 0885-8993, doi: 10.1109/TPEL.2010.2093153
13) M. Bagatin, S. Gerardin, A. Paccagnella, A. Visconti, “Impact of Technology Scaling on the Heavy-ion Upset Cross Section of Multi-Level Floating Gate Cells,” IEEE Transactions on Nuclear Science, Volume 58 (3), June 2011, pp. 969 – 974
14) S. Gerardin, M. Bagatin, A. Paccagnella, A. Visconti, E. Greco, “Heavy-Ion Induced Threshold Voltage Shifts in Sub 70-nm Charge-Trap Memory Cells,” IEEE Transactions on Nuclear Science, Volume 58 (3), June 2011, pp. 827-833
15) L. Sterpone, M. Violante, A. Panariti, A. Bocquillon, F. Miller, N. Buard, A. Manuzzato, S. Gerardin, A. Paccagnella, “Layout-Aware Multi-Cell Upsets Effects Analysis on TMR Circuits Implemented on SRAM-Based FPGAs,” IEEE Transactions on Nuclear Science, Volume 58 (5), October 2011, pp. 2325-2332
16) M. Bagatin, S. Gerardin, A. Paccagnella, “Effects of Total Ionizing Dose on the Retention of 41-nm NAND Flash Cells,” IEEE Transactions on Nuclear Science, Volume 58 (6), December 2011, pp. 2824-2829