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JFET Models (both N and P Channel)

Type Names: njf, pjf

There are two JFET models available, selectable with the level parameter given in the list of model parameters. If level=2 is given, the Parker-Skellern JFET model from Macquarie University in Sydney, Australia will be used. Parameters given must apply to that model. Documentation for this model is available from the Whiteley Research web site, or from
http://www.elec.mq.edu.au/cnerf/spice/spice.html.

If no level parameter is given, or is set to something other than 2, the standard SPICE3 JFET model will be used. This JFET model is derived from the FET model of Shichman and Hodges. The dc characteristics are defined by the parameters vto and beta, which determine the variation of drain current with gate voltage, lambda, which determines the output conductance, and is, the saturation current of the two gate junctions. Two ohmic resistances, rd and rs, are included. Charge storage is modeled by nonlinear depletion layer capacitances for both gate junctions which vary as the -1/2 power of junction voltage and are defined by the parameters cgs, cgd, and pb. The fitting parameter b is a new addition, see[7].

The parameters marked with an asterisk in the area column scale with the area parameter given in the device line.

JFET Model Parameters
name area parameter units default example
vto   threshold voltage V -2.0 -2.0
beta * transconductance parameter A/V2 1.0e-4 1.0e-3
lambda   channel length modulation parameter 1/V 0 1.0e-4
rd * drain ohmic resistance $ \Omega$ 0 100
rs * source ohmic resistance $ \Omega$ 0 100
cgs * zero-bias G-S junction capacitance F 0 5pf
cgd * zero-bias G-D junction capacitance F 0 1pf
pb   gate junction potential V 1 0.6
is * gate junction saturation current A 1.0e-14 1.0e-14
b   doping tail parameter - 1 1.1
kf   flicker noise coefficient - 0 -
af   flicker noise exponent - 1 -
fc   coefficient for forward-bias depletion capacitance formula - 0.5 -
tnom   parameter measurement temperature C 25 50


next up previous contents index
Next: MESFETs Up: Semiconductor Devices Previous: Junction Field-Effect Transistors (JFETs)   Contents   Index
Stephen R. Whiteley 2017-11-08