A robust and physically based compact SOI-LDMOS model

In this paper a physically based compact model is presented which incudes the specific aspects of an SOI-LDMOS transistor, like the lateral doping gradient in the channel and the effect of the gate extending over the drift region.To have an accurate description at all bias conditions, the model is formulated in terms of surface potentials. In contract o circuit-evel models, the so-called internal drain voltage is solved analytically in terms of the terminal voltages. The resulting compact model thus combines the benefits of short comutation times and robustness of explicitly formulated models with accuracy. A comparison with date measured on tansistors of different dimensions and operating temperatures shows that the model provides an accurate well scaled description in al regimes of operation. Since all model expressions and their derivatives are continuous the use of this compact model demonstrates improved convergence in circuit simulation

Transient behaviour and stability points of the Poiseuille flow of a KBKZ-fluid

The Poiseuille flow of a KBKZ-fluid, being a nonlinear viscoelastic model for a polymeric fluid, is studied. The flow starts from rest and especially the transient phase of the flow is considered. It is shown that under certain conditions the steady flow equation has three different equilibrium points. The stability of these points is investigated. It is proved that two points are stable, whereas the remaining one is unstable, leading to several peculiar phenomena such as discontinuities in the velocity gradient near the wall of the pipe (spurt) and hysteresis. Our theoretical results are confirmed by numerical calculationsof the velocity gradient

Traveling waves along viscous filaments

In this article, deflections of a viscous filament in a classical fiber spinning set-up are analyzed. The deflections are considered in a direction perpendicular to the vertical equilibrium state of the spin line. The result is a traveling wave equation with non-uniform coefficients representing the non-uniform filament velocity and non-uniform tension in the spin line. Under neglect of air drag, the system is conservative with respect to an energy functional, so that its eigenmodes have purely imaginary characteristic values. A numerical analysis of the eigenmodes of the system reveals that deflections propagate from take-up wheel to spinneret, with frequencies being multiples of a basic frequency and amplitudes sinus shaped with the maximum being shifted toward the spinneret. From the numerical results, a formula is derived, which approximates the basic frequency and traveling wave velocity directly in terms of the spinning process parameters. Keywords: Deflection – Eigenmode – Fiber spinning – Frequency – Traveling wave – Viscous filament – Viscous string mode

New fundamental insights into capacitance modeling of laterally nonuniform MOS devices

In compact transistor modeling for circuit simulation, the capacitances of conventional MOS devices are commonly determined as the derivatives of terminal charges, which in their turn are obtained from the so-called Ward-Dutton charge partitioning scheme. For devices with a laterally nonuniform channel doping profile, however, it is shown in this paper that no terminal charges exist from which the capacitances can be derived. Instead, for such devices, a new model is presented for the capacitances themselves. Furthermore, a method is given to incorporate such a capacitance model into circuit simulators, which are traditionally based on terminal charge models. Comparison with two-dimensional device simulations and a segmentation model shows that for a constant mobility, the new capacitance model provides an accurate description for a MOSFET with a laterally diffused channel doping profile. Through a comparison with high-frequency measurements, the agreement between model and experimental results is discussed

Capacitance modeling of laterally non-uniform MOS devices

In compact transistor modeling for circuit simulation, the capacitances of conventional MOS devices are commonly determined as the derivatives of terminal charges, which on their turn are obtained from the so-called Ward-Dutton charge partitioning scheme (Ward, 1981). For devices with a laterally non-uniform channel doping profile, however, it is shown in this paper that: 1) no terminal charges exist for the description of capacitances. Instead, 2) a model is presented for the capacitances of such devices, including numerical results for a MOS transistor with a laterally diffused channel doping profile. Finally, 3) a method is given to incorporate such a capacitance model in circuit simulators which are traditionally based on terminal charge models