Small-signal high-frequency performance of power MOS transistors

The performance of power MOS transistor in high frequency linear applications is investigated in this paper. In particular, a model relating structural and layout parameters is developed and used to investigate the characteristics and limitations of the devices and to establish which device offers the best high frequency performance.     

Hedging Point for Non-Markovian Piecewise Deterministic Production Processes

We consider a single non-markovian failure prone machine which delivers a single product. The operating policy of the machine is chosen to be of the hedging point type. In the infinite horizon limit, we calculate the position of the hedging point that minimizes a convex cost function.     

Characterization of glass-ceramic corrosion and durability

The chemical durability of some selected glass-ceramic materials based on the Li₂O- (MnO, CaO)MgO---Al₂O₃---SiO₂ glass composition, has been determined by HCl, using the powder test.

The leachability of the glass-ceramic was gradually increased by replacing MgO with MnO, while it was decreased by addition of MnO instead of CaO. Calcium oxide had a retarding effect on the durability of the material when it was added instead of MgO and/or MnO. However, on the addition of Al₂O₃ in replacing Li₂O, the durability of the material was markedly improved. The leaching data were found to be dependent mainly on the proportion of the glass oxide constituents i.e. MgO/MnO, CaO/MnO and Li₂O/Al₂O₃ ratios present in the glasses.

The results were correlated to different views concerning the effect of various ions on the rate of interdiffusion between the crystalline-glass materials and leaching solution, the type, and proportions of the crystalline phases developed in glass-ceramics and residual glass phase.     

GaAs MESFET differential pass-transistor logic

Two GaAs MESFET implementations of differential pass-transistor logic (DPTL) are presented. The DPTL logic technique combines the area efficiencies and high operation speeds of ratioless pass-transistor circuits with the additional features of noise immunity and low power dissipation. Circuit structures are presented for both depletion (D)-mode and enhancement/depletion (E/D)-mode MESFET technologies, and are compared with buffered FET logic (BFL) and direct-coupled FET logic (DCFL), respectively. Experimental results are provided to verify the functionality and the performance features of both DPTL forms     

GaAs dynamic memory design

Subthreshold leakage loss is a serious problem for GaAs dynamic memory. Since the leakage current in a MESFET is several orders of magnitude higher than that in a MOSFET, it is difficult to retain the charge at dynamic nodes resulting in data storage errors, In order to solve this problem, a novel DRAM architecture is proposed. The design is based on a cell consisting of a MESFET switch and a metal-insulator-metal (MIM) planar capacitor as the storage element. The leakage current is reduced by a level-shift technique and a self-biased transistor is used to maintain the dynamic charge during the sense period. A high performance sense amplifier is used to detect small bit line voltage changes and refresh the stored data. A 1 Kb prototype, fabricated in a 1 μm nonself-aligned GaAs MESFET technology, exhibited a total read/write access time of the order of 3 ns     

A charge-transfer-device logic cell

A logic scheme capable of performing AND-OR logic functions using charge-transfer devices is presented in this paper. Applications of the logic cell are discussed. A half-adder, a ‘flip-flop’, a majority logic gate, an analog-to-digital and a digital-to-analog converter are obtained by extending or modifying the basic scheme. An integrated MOS BBD realization of the AND-OR logic cell is described in detail. Experimental results are presented and shown to be in agreement with theoretical calculations.     

Solid solution phases from thermally crystallized Li2O-MgO-Al2O3-SiO2 glasses

Phase transformations have been studied in glasses related in composition to Li₂O-MgO-SiO₂ (930° C) eutectic glass modified by $\text{Al}{}_2\text{O}{}_3\text{Li}{}_2\text{O}$ replacement on a cation per cation basis. Crystallization processes and changes in the solid solutions of the mineral phases developed during the controlled heating of the glasses have been followed using X-ray and microscopic techniques.Solid solutions of lithia aluminosilicate phases (B-eucryptite and/or B-spodumene s.s.) are the essential minerals that crystallize in glasses through most of the heat treatment applied. Lithium metasilicate, disilicate, clinoenstatite and cordierite are also encountered.B-eucryptite s.s. is formed in early stage of crystallization of the glass which transforms into B-spodumene s.s. at higher temperature (800° C). However, in some cases, it persists at temperatures as high as 1000° C.Metastable B-eucryptite-B-quartz s.s. can accomodate considerable amounts of Mg²⁺ and Al³⁺ ions in its lattice especially at lower temperature. At higher temperature for long duration, a redistribution of the elements takes place, and the cordierite phase then developed.     

Application of computer techniques and aerospace sciences as a means for quality control in rockets industry

Tactical requirements of an artillery rocket normally specify its dispersion on the ground in order to achieve a desired weapon effectiveness. Such dispersion is generally affected by manufacturing tolerances as well as rocket response to external disturbances.Specifying appropriate system tolerances always represents a difficult design problem, especially during the contracting phase of the first batch of mass production. The present paper discusses a statistical approach to this problem.Statistical correlations between sensitivity parameters of rocket's range dispersion and its technical specifications are established based on the available data about international systems currently in service. Eventually, the conclusions of the study are reduced to a design procedure for similar situations.