In this article we’ ll see how to find the parameters used to describe the mathematical behaviour of JFET (Junction Field Effect Transistors).The syntax for the N-channel model is:

model ModelName NJF( par1=a par2=b………parn=x)

while for the P-channel model is:

model ModelName PJF( par1=a par2=b………parn=x)

Where par1 par2… parn are the parameters that allow us to model the equations of the JFET transistor.

The main parameters for modeling the JFET are listed below in this table:

 

Parameters	Description	Units	Default Value
AF	Flicker noise exponent	no unit dimension	1.0
ALPHA	Ionization coefficient	1/V	1e-006
BETA	Transconductance coefficient	A/V^2	0.0001
BETATCE	BETA exponential temperature coefficient	%/°C	-0.5
CGD	Zero-bias gate-drain p-n capacitance	F	1e-012
CGS	Zero-bias gate-source p-n capacitance	F	1e-012
FC	Forward-bias depletion capacitance coefficient	no unit dimension	0.5
IS	Gate p-n saturation current	A	1e-014
ISR	Gate p-n recombination current parameter	A	0
KF	Flicker noise coefficient	no unit dimension	1e-018
LAMBDA	Channel-length modulation	1/V	1e-006
M	Gate p-n grading coefficient	no unit dimension	0.5
N	Gate p-n emission coefficient	no unit dimension	1.0
NR	Emission coefficient for ISR	no unit dimension	2.0
PB	Gate p-n potential	V	1.0
RD	Drain ohmic resistance	Ohm	1.0
RS	Source ohmic resistance	Ohm	1.0
VK	Ionization knee voltage	V	1.0
VTO	Thresold voltage	V	-2.0
VTOTC	VTO temperature coefficient	V/°C	-0.0025
XTI	IS temperature coefficient	no unit dimension	3.0