Laboratoire Ampere

Capelle, France

Laboratoire Ampere

Capelle, France
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Nicol G.W.,Laboratoire Ampere | Bayer B.,Limnology and Bio Oceanography | Spieck E.,Biocenter Klein Flottbek | Thomm M.,Lehrstuhl For Mikrobiologie Und Archaeenzentrumuniversitat Regensburgregensburg93053 Germany | And 2 more authors.
Environmental Microbiology | Year: 2017

Thaumarchaeota are globally distributed and abundant microorganisms occurring in diverse habitats and thus represent a major source of archaeal lipids. The scope of lipids as taxonomic markers in microbial ecological studies is limited by the scarcity of comparative data on the membrane lipid composition of cultivated representatives, including the phylum Thaumarchaeota. Here, we comprehensively describe the core and intact polar lipid (IPL) inventory of ten ammonia-oxidising thaumarchaeal cultures representing all four characterized phylogenetic clades. IPLs of these thaumarchaeal strains are generally similar and consist of membrane-spanning, glycerol dibiphytanyl glycerol tetraethers with monoglycosyl, diglycosyl, phosphohexose and hexose-phosphohexose headgroups. However, the relative abundances of these IPLs and their core lipid compositions differ systematically between the phylogenetic subgroups, indicating high potential for chemotaxonomic distinction of thaumarchaeal clades. Comparative lipidomic analyses of 19 euryarchaeal and crenarchaeal strains suggested that the lipid methoxy archaeol is synthesized exclusively by Thaumarchaeota and may thus represent a diagnostic lipid biomarker for this phylum. The unprecedented diversity of the thaumarchaeal lipidome with 118 different lipids suggests that membrane lipid composition and adaptation mechanisms in Thaumarchaeota are more complex than previously thought and include unique lipids with as yet unresolved properties. © 2017 Society for Applied Microbiology and John Wiley & Sons Ltd.

Dubois F.,INSA Lyon | Dubois F.,Laboratoire Ampere | Dubois F.,Safran Group | Morel H.,Safran Group | And 3 more authors.
Proceedings - IMAPS International Conference and Exhibition on High Temperature Electronics, HiTEC 2012 | Year: 2012

This paper presents a qualitative description of the punch-through mechanism in Silicon Carbide (SiC) JFET from Infineon/SiC ED. A detailed one-dimensional analytical expression is derived for the current-voltage characteristic of the punch-through effect in the SiC JFET. The proposed model based on physical parameters is validated with experimental results for low current level.

Asllani B.,Laboratoire Ampere | Berthou M.,Laboratoire Ampere | Tournier D.,Laboratoire Ampere | Brosselard P.,CALY Technologies | Godignon P.,CSIC - National Center of Microelectronics
Materials Science Forum | Year: 2016

This paper presents a study of the Schottky barrier evolution on SBD and JBS diodes over a wide range of temperatures from 80 to 500 K. We show that inhomogeneities of the Schottky contact have a strong impact on the dependence of barrier characteristics with temperature, especially below 200 K. Analysis of the reverse bias current of such diodes at low temperature show that the barrier height depends on temperature but also on voltage. © 2016 Trans Tech Publications, Switzerland.

Larousse S.,Lyon Institute of Nanotechnologies | Razik H.,Laboratoire Ampere | Cellier R.,Lyon Institute of Nanotechnologies | Lombard P.,Lyon Institute of Nanotechnologies | Volay P.,Centralp
9th International Conference on Power Electronics - ECCE Asia: "Green World with Power Electronics", ICPE 2015-ECCE Asia | Year: 2015

This article presents a modified control strategy for a large input voltage range in an active-clamp soft switching converter. This control strategy is based on frequency modulation and allows a soft switching of all semiconductor devices on a large input voltage range. This frequency modulation also minimizes transformer loss without losing soft switching both on primary and secondary side of the converter. The proposed control strategy was implemented on a 30W prototype with a switching frequency up to 215kHz. The prototype is soft switching on an input voltage range between 15V and 75V, confirming the benefits of the presented control strategy with efficiency above 90% on a 28-63V range. © 2015 Korean Institute of Power Electronics.

Degrenne N.,Laboratoire Ampere | Marian V.,Laboratoire Ampere | Vollaire C.,Laboratoire Ampere | Buret F.,Laboratoire Ampere | And 2 more authors.
IEEE Antennas and Wireless Propagation Letters | Year: 2012

Rectifying antenna (rectenna) associations can be advantageously used to harvest electromagnetic energy from different directions. When the rectennas are associated in series, their output voltages are added, and the electrical dc energy is more easily exploitable. This letter shows that if a rectenna receives significantly less energy than the others (i.e., unbalanced association), its voltage polarity may reverse. Simulation and experimental results show that when an unbalanced association is operated at maximum power point, voltage reversal can result in a total decrease in efficiency of up to 26%. Possible solutions to reduce these detrimental consequences are also discussed. © 2012 IEEE.

Berthou M.,CSIC - National Center of Microelectronics | Godignon P.,CSIC - National Center of Microelectronics | Montserrat J.,CSIC - National Center of Microelectronics | Millan J.,CSIC - National Center of Microelectronics | Planson D.,Laboratoire Ampere
Journal of Electronic Materials | Year: 2011

Tungsten is a suitable metal contact for high-temperature applications. We fabricated 1.7-kV and 6-kV 4H-SiC junction barrier Schottky (JBS) diodes with a tungsten Schottky contact with different geometries, and their forward characteristics were measured up to 300°C. The 1.7-kV diodes exhibited unipolar conduction up to 6 V at 275°C, whereas 6-kV diodes showed ideal on-resistance, R on. An optimized JBS design permits a higher breakdown voltage to be obtained than for the pure Schottky diode, with a reasonable increase (10%) of the on-resistance. Results demonstrate the feasibility of tungsten JBS diodes for fast-switching, high-voltage, and high-temperature applications. © 2011 TMS.

Berthou M.,Laboratoire Ampere | Bevilacqua P.,Laboratoire Ampere | Fonder J.B.,Laboratoire Ampere | Tournier D.,Laboratoire Ampere
Materials Science Forum | Year: 2016

SiC MOSFET are now commercially available and show promising performances when considering static losses, commutations and long term reliability. The devices may face short-circuit conditions, and knowing their capability in terms of critical conditions and repetitive fault is mandatory before integration in commercial systems. This paper presents the short-circuit performances for two families of commercial devices in terms of critical energy, time and repetitive SC stress. It shows that both devices exhibit similar critical time at different biases. However, they show very different behaviour when stressed under repetitive SC pulses. These results demonstrate that SiC MOSFET reliability under repetitive short-circuit pulses strongly depends on the pulse length and device provider. This information will be crucial to design the system in order to limit the SC length depending on the application requirements. © 2016 Trans Tech Publications, Switzerland.

Gaignaire R.,University of Liège | Scorretti R.,Laboratoire Ampere | Sabariego R.V.,University of Liège | Geuzaine C.,University of Liège
IEEE Transactions on Magnetics | Year: 2012

The finite element method can be used to compute the electromagnetic fields induced in the human body by environmental extremely low frequency (ELF) fields. However, the electric properties of tissues are not precisely known and may vary depending on the individual, his/her age and other physiological parameters. In this paper, we account for the uncertainties on the conductivities of the brain tissues and spread them out to the induced fields by means of a nonintrusive approach based on Hermite polynomial chaos, with the finite element method as a black box. After showing the convergence of the method, we compute the probability to be over the thresholds defined by the international guidelines for limiting exposure to electromagnetic fields published by ICNIRP. © 2012 IEEE.

Berthou M.,Laboratoire Ampere | Asllani B.,Laboratoire Ampere | Brosselard P.,Laboratoire Ampere | Godignon P.,CSIC - National Center of Microelectronics
Materials Science Forum | Year: 2015

W-SBD show exceptional reliability from 200 to 500K, however, its barrier analysis has never been performed thoroughly down 81K. This paper shows our study of Schottky barrier and Richardson coefficient, both extracted for different temperature ranges. We observed fluctuation in function of the temperature. We analyse this phenomenon and compare it to literature for other barriers. Measurements of reverse characteristics up to 1200V have been performed from 81 to 450K. It confirms that partial ionization influence on the drift doping impacts on the barrier height. © (2015) Trans Tech Publications, Switzerland.

Berthou M.,Laboratoire Ampere | Planson D.,Laboratoire Ampere | Tournier D.,Laboratoire Ampere
Materials Science Forum | Year: 2015

This paper presents our study of SiC MOSFETs, JFETs and BJT under capacitive load short-circuit up to 600V. BJTs show heterogeneous results due to unstable technology. In the contrary MOSFETs critical short circuit show bus voltage dependency with critical time of about 10μs at 600V. The failure is repetitive and characterized by a gate to source short-circuit due to self-heating. On the other hand, LV-JFET device, despite its normally-on disadvantage and higher resistivity, and thanks to its current limiting capability, shows superior SC capability with critical time over 600μs at 600V. Exploitation of this feature allowed us to produce a current limiter prototype capable to strongly limit the current in order to stand short-circuit during 200ms at 400V. © (2015) Trans Tech Publications, Switzerland.

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