Symbolic charge-based MOSFET model
C. Galup-Montoro and M.C. Schneider
Federal University of Santa Catarina, BR
MOSFET compact model, symbolic model, circuit design
The new generation of compact MOSFET models provides accurate current, charge, capacitance and noise characteristics as numerical outputs of a rather complicated set of internal equations specific to each model. Clearly, numerical circuit simulation is a fundamental tool for circuit verification, but is not really useful in the early stages of design. Very simple models of the transistors are customary used at these stages, but they are not accurate, particularly for advanced technologies. This work aims to furnish new precise and complete symbolic models of the MOS transistor useful for the early stages of design. The main idea is to preserve the simple formalism of strong inversion, but with the use of a new virtual charge variable render it capable of describing the actual transport including diffusion and limit velocity effects.
We adopt the following definition for the virtual charge: The drift of the virtual charge produces the same current as the actual movement of the real charge which includes drift, diffusion and limit velocity.
We will show that: The virtual charge is the real inversion charge plus the pinch-off charge (diffusion increases the current) minus the saturation charge (limit velocity reduces the current).
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Nanotech 2006 Conference Program Abstract