Search results for "VOLTAGE"
showing 10 items of 934 documents
Performance of sensl C-Series SiPM with high photoelectron resolution at cryogenic temperatures
2016
The C-Series of silicon photomultipliers (SiPM) from SensL provides devices with a fast response and high performance at low cost. The device's ability to detect light at temperatures of liquid nitrogen (77K) and liquid helium (4 K) with high photoelectron resolution was demonstrated. Results include relative photon detection efficiency (PDE), gain, microcell capacitance, and cross-talk probability at different over-voltages, both at room and at cryogenic temperatures. At 77K the SiPM demonstrated significantly improved operating characteristics while at 4K the observed increase in break-down voltage, the reduction of PDE by a factor of 2-3, and the extensively dropped microcell capacitance…
Effect of driving method on the degradation of organic light emitting diodes
2003
Abstract Lifetime testing results are reported for organic light emitting diodes (OLEDs) having the structure ITO (anode)/ N , N ′-diphenyl- N , N ′-bis(3-methylphenyl)-1,1′-diphenyl-4,4′-diamine (TPD)/tris-(8-hydroxyquinoline)aluminum (AlQ)/Al (cathode) and operated using dc and pulsed waveforms for comparison. In ambient atmosphere non-encapsulated devices show a lifetime of about 70 h in pulsed operation at an initial luminance of 500 cd/m 2 , almost four times longer than in dc operation. A fast initial decay of luminance is observed for dc operation. It is most probably due to a combination of Joule heating and mobile ionic impurities migration within the OLED structure under the conti…
Feedback Biasing Based Adjustable Gain Ultrasound Preamplifier for CMUTs in 45nm CMOS
2018
As CMOS technology is scaled down, supply voltages are decreasing and intrinsic gain of the nanoscale CMOS transistors is dropping while the threshold voltages of transistors are remaining relatively constant. In such scaled down nanoscale CMOS technologies, conventional vertical stacking architectures (for example. cascode architectures) for high-gain becomes no more attractive. In this paper we present the analysis and design of a feedback biasing based adjustable gain ultrasound preamplifier which is capable of amplifying signals from 15 MHz to 45 MHz from Capacitive Micromachined Ultrasound Transducers (CMUTs) in 45nm CMOS technology for medical ultrasound imaging applications. From the…
Scattering and Depolarization in a Polymer Dispersed Liquid Crystal Cell
2008
An imaging polarimeter in transmission has been used to explore the effects of scatter and depolarization induced by a polymer dispersed liquid crystal cell. The experiment was carried out for three visible wavelengths. Both a directional and a scattered component can be distinguished in the light transmitted by this material. Whereas the directional component increased with voltage, the scattered portion decreased. This was a common behaviour for all three wavelengths. The polarimetric analysis revealed that the degree of polarization was also affected by changes in the voltage applied to the cell. Depolarization effects in the scattered component were usually high and decreased with volta…
Hot carrier effects in n-MOSFETs with SiO2/HfO2/HfSiO gate stack and TaN metal gate
2009
Charge trapping and trap generation in field-effect transistors with SiO2/HfO2/HfSiO gate stack and TaN metal gate electrode are investigated under uniform and non-uniform charge injection along the channel. Compared to constant voltage stress (CVS), hot carrier stress (HCS) exhibits more severe degradation in transconductance and subthreshold swing. By applying a detrapping bias, it is demonstrated that charge trapping induced degradation is reversible during CVS, while the damage is permanent for hot carrier injection case. © 2008 Elsevier B.V. All rights reserved.
Design and analysis of filament power supply method for increasing life time of thermal emission tubes
2017
This paper has reviewed power supply methods for thermal electron tubes and proposes a method for purpose of increasing its lifetime, with reducing complexity of circuit and, improvement in power efficiency. In this work, the filament is operated with a decreased voltage level while maintaining the output anode power at the same level as required for the filament's operation at nominal voltage. The supply circuit is designed to avoid the reduction of filament voltage below a minimum level. A power converter made of thyristors and rectification diodes is designed to supply the filament voltage. Converter is carefully monitored and controlled by an algorithm embedded in a contemporary Digital…
Electrical connections and driving electronics for piezo-actuated x-ray thin glass optics
2016
Use of thin glass modular optics is a technology currently under study to build light, low cost, large area X-ray telescopes for high energy astrophysics space missions. The angular resolution of such telescopes is limited by local deviations from the ideal shape of the mirrors. One possible strategy to improve it consists in actively correcting the mirror profile by gluing thin ceramic piezo-electric actuators on the back of the glasses. A large number of actuators, however, requires several electrical connections to drive them with the different needed voltages. We have developed a process for depositing conductive paths directly on the back of non-planar thin foil mirrors by means of a p…
Study and design of a controlled oscillator for an embedded system to measure the complex impedance of PEM fuel cell »
2017
We present in this paper the study and the design of a voltage controlled oscillator (VCO) for an embedded system to diagnose the PEM fuel cell. Some problems related to fuel cells used in the electric vehicle field are the management of its efficiency and the lifetime of its membranes. To do this, the diagnosis using measuring the complex impedance is an important phase. It is based on the injection of a perturbation signal at the output of the PEM fuel cell, then we observe its behavior by measuring its impedance. The used measurement method is the electrochemical impedance spectroscopy (EIS) using the load modulation technique, which is implemented in an embedded measurement system based…
<title>Long-term testing results of WO<formula><inf><roman>3</roman></inf></formula>-based electrochromic c…
1997
Two batches of the samples of electrochromic cell with WO3 and IrOx electrodes and Sb2O5 (DOT) water based solid electrolyte were tested at constant contrast ratio up to 107 cycles or stored during five years and the changes of current-voltage characteristics were studied. Two kinds of the changes were observed. The shift of curves along the voltage axis is supposed to be associated with the changes in the oxidation degree of tungsten oxide, while the changes in their shapes are associated with changes of water content in pores. The processes in the samples during cycling and storing are discussed.© (1997) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the…
Investigation of recovery mechanisms in dye sensitized solar cells
2016
Abstract We study the spontaneous recovery phenomenon displayed by solar cells sensitized with a ruthenium complex-based dye N719, which manifests with the increase over the time (from several minutes up to some days) of the short circuit current density J sc and the open circuit voltage V oc , during cell illumination. Under dark conditions the current decreases over time after the application of forward bias voltages. We investigate the effects of temperature and electrolyte composition by means of current–voltage measurements and electrochemical impedance spectroscopy, both under dark and illumination conditions. The main result is that the recovery of the performances depends on the cha…