The Real Transistor
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The basic E.K.V. model considered in the previous chapter is not suited for real transistors for it makes use of the “gradual channel” approximation, like the C.S.M. Non-uniform doping, mobility degradation, short channel effects, etc. are ignored. Advanced models like BSIM and PSP, which are primarily circuit simulation tools, take care of these but don’t offer the degree of flexibility that is desirable.
We show in this chapter that as long as the source and drain voltages with respect to the substrate remain constant, DC currents, g m ∕ I D and g d ∕ I D ratios of real transistors, even sub-micron devices, can be reconstructed by means of the basic E.K.V model. Once V S or V D is modified, the parameters must be updated. The model remains unchanged however.