.BondLib.Spice.Utilities.CjJ

Information

The Spice-style junction capacitance for JFETs and GaAs MESFETs computes the depletion and diffusion capacitance values of a junction used in a JFET / MESFET. 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. 

Parameters:

 Level:   JFET modeling level (default value = 1)
            Level=1: Shichman-Hodges (Si) JFET model
            Level=2: Improved Shichman-Hodges (Si) JFET model [2]
            Level=3: Statz-Curtice (GaAs) MESFET model [3,4]

 Tnom:    Reference temperature (default value = 300.15 K)

 VT0:     Threshold voltage at reference temperature (default value = 0 Volt)

 IS:      Transport saturation current (default value = 1e-14 Amp)

 TCV:     Linear temperature coefficient of threshold voltage (default value = 0 Volt/K)

 EG:      Energy gap for temperature effect on saturation current at 0 K
            default value = 1.11 Volt for Levels=1,2 (Si)
            default value = 0.73 Volt for Level=3 (GaAs)

 N:       Current emission coefficient (default value = 1)

 XTI:     Saturation current temperature exponent
            default value = 3 for Levels=1,2 (Si)
            default value = 2 for Level=3 (GaAs)

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

 CGS:     Zero-bias gate-source depletion capacitance at reference temperature (default value = 0.5e-12 F)

 CGD:     Zero-bias gate-drain depletion capacitance at reference temperature (default value = 0.5e-12 F)

 M:       Junction grading coefficient
            default value = 0.33 for Levels=1,2 (Si)
            default value = 0.5  for Level=3 (GaAs)

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

 TT:      Ideal transit time (default value = 5e-9 sec)

 ALPHA:   Hyperbolic tangient fitting parameter (default value = 1)

 DELTA:   Voltage range for transition (default value = 0.2 Volt)

 VMAX:    Limit voltage for carrier velocity saturation (default value = 0.5 Volt)

 GminDC:  Leakage conductance (default value = 1e-15 Mho)

 Area:    Relative area occupied by the diode (default value = 1)

 GS:      True if gate-source junction (default value = true)

 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.153.
  3. Massobrio, G. and P. Antognetti (1993), Semiconductor Device Modeling with Spice, 2nd edition, McGraw Hill, New York, p.382.
  4. Statz, H., P. Newman, I.W. Smith, R.A. Pucel, and H.A. Hans (1987), "GaAs FET Device and Circuit Simulation in Spice," IEEE Trans. Electron Devices, 34(2), pp. 160-169.
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