A SOS MOSFET SPICE model for confident analogue circuit design

The authors present details of a charge-based circuit simulation model which is continuous from subthreshold to strong inversion and is therefore suitable for analog design. The model has been implemented in the SPICE2 program. The model equivalent circuit is shown, and a set of simulated subthreshold characteristics for an n-channel device is presented. The current is smooth and continuous from cutoff through subthreshold to strong inversion, and the influence of the kink effect can be seen in increasing the inverse subthreshold slope with increasing drain bias. Sample capacitance characteristics are illustrated, and these are also smooth and continuous into subthreshold, allowing accurate small-signal simulation and enhancing convergence in transient simulation. Good modeling of the drain conductance is achieved throughout the kink region, ensuring correct prediction of circuit small-signal gain. In the frequency domain, the model predicts the correct behavior of drain admittance, which is particularly important in analog design. The typical measured threshold shift dependence on total radiation dose is also illustrated.<
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