(J) JFET Statement

We support the standard SPICE junction field-effect transistor (JFET) model [1] [2]. We have made minor improvements to the PN-junction currents in reverse bias to ensure continuity of the modeling equations.

Jname drain gate source modelName <<AREA>=area> <IC=vds,vgs> <TEMP=temp> <M=m>
.MODEL modelName NJF <NAME=value ...>

Jname drain gate source modelName <<AREA>=area> <off> <IC=vds,vgs> <TEMP=temp> <M=m>
.MODEL modelName NJF <NAME=value ...>

By default, an initial guess of \(V_{\text{gs}} = V_{\text{gd}} = -1\,\text{V}\) (\(1\,\text{V}\)) is used in the operating point analysis for a NJF-type (PJF-type) JFET. When the off flag is set, an initial guess of zero is used instead. Note that this option does not enforce a constraint on the solution found during the operating point analysis.

  • The JFET device type NJF or PJF must be specified in the model statement.

  • You can customize this model by providing a list of model parameter (name-value format) at the end of the .MODEL statement.

Instance Parameters

Parameter

Description

Default Value

AREA

Device area (number of parallel devices)

\(1\)

IC

Initial condition voltages (\(V_{\text{ds}}, V_{\text{gs}}\)).

none

TEMP

Device temperature

\(27\,^\circ\text{C}\)

M

Number of parallel devices

\(1\)

  • When the IC parameter is given, initial values for both the drain-source (\(V_{\text{ds}}\)) and the gate-source voltage (\(V_{\text{gs}}\)) must be specified.

Model Parameters

Parameter

Value

Default Value

T_ABS

Device temperature

\(27\,^\circ\text{C}\)

TNOM

Nominal temperature

\(27\,^\circ\text{C}\)

VTO

Threshold voltage

\(-2\,\text{V}\)

BETA

Transconductance

\(10^{-4}\,\text{A}/\text{V}^2\)

LAMBDA

Channel length modulation

\(0\,\text{V}^{-1}\)

B

Parker-Skellern fit parameter (Doping tail parameter)

\(1\)

IS

Reverse saturation current for the gate-source and gate-drain junctions

\(10^{-14}\,\text{A}\)

XTI

Temperature exponent for IS

\(1\)

EG

Band gap energy

\(1.11\,\text{eV}\)

N

Emission coefficient for the gate-source and gate-drain junctions

\(1\)

PB

Gate junction potential

\(1\, \text{V}\)

M

Gate junction grading coefficient

\(0.5\)

CGS

Gate-source zero-bias junction capacitance

\(0\,\text{F}\)

CGD

Gate-drain zero-bias junction capacitance

\(0\,\text{F}\)

FC

Forward-bias depletion capacitance coefficient

\(0.5\)

RS

Source resistance

\(0\, \Omega\)

RD

Drain resistance

\(0\, \Omega\)

  • The instance parameter TEMP overwrites the model parameter T_ABS.

  • The parameters representing currents and capacitances (starting with I and C) are multiplied by the AREA parameter.

  • The parameters representing resistances (starting with R) are divided by the AREA parameter.

  • The parameter BETA is multiplied by the device area.

Note

  • Some parameters encountered in semiconductor models are provided as additional information and do not affect the simulation. PLECS Spice ignores the following parameters: mfg.

Examples

J1 drain gate source nJFet
.MODEL nJFet NJF VTO=-2 BETA=1e-3 LAMBDA=0.01 RD=10 RS=10

References