Junction FET

In this topic:

Netlist Entry

Jxxxx drain gate source modelname [area] [OFF] [IC=vds,vgs]
+ [TEMP=local_temp] [M=mult] [DTEMP=dtemp]
drain Drain node
gate Gate node
source Source node
modelname Name of model defined in a .model statement. Must begin with a letter but can contain any character except whitespace and period '.'.
area Area multiplying factor. Area scales up the device. E.g. an area of 3 would make the device behave like 3 transistors in parallel. Default is 1.
OFF Instructs simulator to calculate operating point analysis with device initially off. This is used in latching circuits such as thyristors and bistables to induce a particular state. See .OP for more details.
vds,vgs Initial conditions for drain-source and gate-source junctions respectively. These only have an effect if the UIC parameter is specified on the .TRAN statement.
local_temp Local temperature. Overrides specification in .OPTIONS or .TEMP statements.
mult Device multiplier. Equivalent to putting mult devices in parallel.
dtemp Differential temperature. Similar to local_temp but is specified relative to circuit temperature. If both TEMP and DTEMP are specified, TEMP takes precedence.

N Channel JFET: Model Syntax

.model modelname NJF ( parameters )

P Channel JFET: Model Syntax

.model modelname PJF ( parameters )

JFET: Model Parameters

The symbols '???MATH???\times???MATH???' and '???MATH???\div???MATH???' in the Area column means that parameter should be multiplied or divided by the area factor respectively.

Name Description Units Default Area
VTO Threshold voltage V -2.0
VTOTC VTO temp coefficient V/???MATH???°???MATH???C 0
BETA Transconductance parameter A/V2 1e-4 ???MATH???\times???MATH???
BETATCE BETA temperature coefficient % 0
LAMDA Channel length modulation parameter 1/V 0
ALPHA Impact ionisation coefficient 0
VK Impact ionisation knee voltage V 0
RS Source ohmic resistance ???MATH???\Omega???MATH??? 0 ???MATH???\div???MATH???
CGS Zero-bias G-S junction capacitance F 0 ???MATH???\div???MATH???
CGD Zero-bias G-D junction capacitance F 0 ???MATH???\div???MATH???
M Grading coefficient 1.0
PB Gate junction potential V 1
IS Gate junction saturation current A 1e-14 ???MATH???\times???MATH???
N Gate junction emission coefficient 1
ISR Recombination current 0
NR ISR emission coefficient
XTI IS temperature coefficient 3
KF Flicker noise coefficient 0
AF Flicker noise exponent 1
FC Coefficient for forward bias depletion capacitance 0.5
NLEV Select noise model 2
GDSNOI Channel noise coefficient. Use with NLEV=3 1.0
TNOM, T_MEASURED Reference temperature; the temperature at which the model parameters were measured ???MATH???°???MATH???C 27
T_ABS If specified, defines the absolute model temperature overriding the global temperature defined using .TEMP ???MATH???°???MATH???C -
T_REL_GLOBAL Offsets global temperature defined using .TEMP. Overridden by T_ABS ???MATH???°???MATH???C 0.0


Q2 is a U430 with a local temperature of 100???MATH???°???MATH???C.