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Thermostable polyimides based on perylenetetracarboxylic dianhydride and aromatic diamines containing oxadiazole rings were prepared and thin films were made therefrom. Dark-red, opaque coatings resulted having strong adhesion to the glass support. The composition of these polyimide films was analysed using X-ray photoelectron spectroscopy (XPS). The dynamo-mechanical and dielectric behaviour of the...
Dielectric and conduction properties of polyimides were evaluated on the basis of dielectric constant, dielectric loss, electric modulus and AC conductivity, and their variation with frequency and temperature. Polyimide films exhibited good insulating properties with dielectric constants values in the range of 2.78–3.48 and dielectric loss comprised between 0.01 and 0.03 at 1Hz at room temperature.
Electrical conductivity and the Hall-effect are investigated in the temperature interval (80–400) K on thermally annealed in H2 CdS thin films obtained by chemical bath deposition. Different characters of the temperature dependence of conductibility are observed in the CdS films annealed at different temperatures. The Hall measurements allow calculating the values of the NA, ND, nex and ED. According...
New polyimides have been synthesized by reaction of 3,3',4,4'-benzophenone tetracarboxylic dianhydride (BTDA) or/and 5-[2,5-(dioxotetrahydrofuryl)]-3-methyl-3-cyclohexen-1,2-dicarboxylic anhydride (DOCDA) with 4,4'-methylene dianiline (DDM). Polycondensation reactions were carried out in solution and resulting polyimides gave flexible free-standing films. The introduction of alicyclic moieties in...
Three ceramic magnetic compositions within the CuZnTi ferrite system, having the Curie temperatures centered around 60°C, 80°C and 100°C, respectively were investigated in order to determine the time-temperature stability of their main magnetic properties. Rates of changes of 33, 66 and 100 ppm/h of the maximum slopes of permeability were found for the samples aged at 60°C, 80°C and 100°C, respectively...
The emerging smart power BCD technologies allow smaller device sizes hence, under the same operating conditions, the device must dissipate the same amount of power on a much smaller area, which leads to a more pronounced self — heating effect. Therefore, accurate prediction of heat dissipation in the DMOS structure, up to thermal runaway, is necessary. We have designed a test structure capable of...
Two architectures of a bandgap reference with CMOS operational amplifiers are investigated, implemented and compared. In order to reduce the dependence of the reference voltage with temperature and power supply, the trimming technique is often used. We propose a new method of lowering the reference voltage variation, based on a very low offset voltage amplifier. Two operational amplifier schematics...
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