BondLib.Electrical.Analog.Spice.Utilities.CjM

# .BondLib.Electrical.Analog.Spice.Utilities.CjM

Spice-style junction capacitor model for MOSFETs

## Information

The Spice-style junction capacitance for MOSFETs computes the depletion capacitance value of a junction used in a MOSFET. Different Spice dialects vary in the formulae they use for this purpose. Many Spice dialects actually don't use a formula for the junction capacitance at all, but rather compute the electric charge stored in the junction directly, which is conceptually cleaner. However, that approach is computationally cumbersome, as it leads to an awkward algebraic loop [1]. Thus, we chose to compute the junction capacitance, and use a (physically incorrect) approximate non-linear capacitor model. The numerical error should remain small, as the time constants associated with temperature variation are much larger than those associated with electrical phenomena.

This particular model uses the capacitance formula advocated in [2].

    Parameters:

     Level:   MOSFET modeling level (default value = 3)
                Level=0: Static injection model
                Level=1: Shichman-Hodges model
                Level=2: Grove-Frohman model
                Level=3: Empirical model
                Level=4: Simplified Grove-Frohman model

     IS:      Transport saturation current (default value = 0 Amp)

     PB:      Built-in potential at reference temperature (default value = 0.8 Volt)

     CJ:      Zero-bias bulk capacitance per square meter at reference temperature (default value = 1e-4 F/m2)

     MJ:      Bulk junction grading coefficient (default value = 0.33)

     CJSW:    Zero-bias perimeter capacitance per meter at reference temperature (default value = 1e-9 F/m)

     MJSW:    Perimeter capacitance grading coefficient (default value = 0.33)

     FC:      Forward-bias depletion capacitance coefficient (default value = 0.5)

     A:       Diffusion area (default value = 0 m2)

     P:       Perimeter width (default value = 0 m)

     EG:      Energy gap for temperature effect on saturation current (default value = 1.11 Volt)

     GminDC:  Leakage conductance (default value = 1e-12 Mho)

     EMin:    if x < EMin, the exp(x) function is linearized (default value = -100)

     EMax:    if x > EMax, the exp(x) function is linearized (default value = 40)

References:

1. Cellier, F.E. (1991), Continuous System Modeling, Springer-Verlag, New York, pp. 224-225.
2. Massobrio, G. and P. Antognetti (1993), Semiconductor Device Modeling with Spice, 2nd edition, McGraw Hill, New York, p.200.

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