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Nexxim Simulator > Nexxim Component Models >
FETs (JFETs and MESFETs) > JFET Model (Level 1)
JFET Model (Level 1)
The .MODEL statement for the Level
1 JFET has the netlist syntax.
.MODEL modelname NJF [LEVEL=1]
[modelparameter=val]
...
or
.MODEL modelname PJF [LEVEL=1]
[modelparameter=val]
...
The entry NJF
selects the N-channel JFET, while PJF
selects the P-channel JFET.
Level 1 and Level 2 JFET
Model Parameters
Model Parameter
|
Description
|
Unit
|
Default
|
LEVEL
|
1 selects the Basic SPICE JFET
model
|
None
|
1 (default if LEVEL parameter is
omitted)
|
ACM
|
Gate area calculation method
|
None
|
0
|
AF
|
Flicker noise exponent
|
None
|
1.0
|
ALIGN
|
Correction for gate misalignment
|
Meter
|
0.0
|
ALPHA (ALFA,
ALPHA1)
|
Saturation factor
|
Volt-1
|
2.0
|
AREA
|
Area factor
|
None
|
1.0
|
BETA
|
Transconductance (gain)
|
Amp/Volt2
|
1.0e-4
|
BEX
|
Temperature exponent to correct
for low field mobility
|
None
|
0.0
|
CAPOP
|
Capacitor model selector
|
None
|
0
|
CAPDS (CDS)
|
Drain-source capacitance
|
Farad
|
0.0
|
CGD
|
Zero-bias gate-drain junction capacitance
|
ACM = 0 : Farad
ACM = 1 :
Farad/Meter2
|
0.0
|
CGS
|
Zero-bias gate-source junction
capacitance
|
ACM = 0 : Farad
ACM = 1 :
Farad/Meter2
|
0.0
|
CRAT
|
Source ratio of gate capacitance
|
None
|
0.666
|
CTD
|
Temperature coefficient for gate-drain
junction capacitance
|
°C-1
|
0.0
|
CTS
|
Temperature coefficient for gate-drain
junction capacitance
|
°C-1
|
0.0
|
DCAP
|
Capacitance equation selector
|
None
|
2
|
EG
|
Energy gap for gate-drain and gate-source
diodes at 0 °K.
|
electron-Volt
|
1.11
|
FC
|
Coefficient for PB in forward-bias
capacitance calculations
|
None
|
0.5
|
GAMDS (GAMMA,
GAMA)
|
Lowering coefficient for drain
voltage-induced threshold voltage
|
None
|
0.0
|
GAP1
|
1st bandgap correction factor
|
electron-Volt/°K
|
7.02e-4
|
GAP2
|
2nd bandgap correction factor
|
°K
|
1108.0
|
GCAP
|
Zero-bias gate capacitance
|
ACM = 0 : Farad
ACM = 1 :
Farad/Meter2
|
Not used if not provided
|
GDSNOI
|
Channel noise coefficient (NLEV
= 3)
|
None
|
1.0
|
HDIF
|
Distance of heavily-doped (low
resistance) region from source or drain contact to lightly-doped region
|
Meter
|
0.0
|
IS
|
Gate junction saturation current.
|
ACM = 0: Amp
ACM = 1:
Amp/Meter2
|
1.0e-14
|
KF (KF4)
|
Flicker noise coefficient
|
None
|
0.0
|
L
|
FET gate length
|
Meter
|
0.0
|
LAMBDA (LAMB)
|
Channel length modulation factor
|
Volt-1
|
0.0
|
LDEL
|
Difference between drawn length
and actual or optical device length
|
Meter
|
0.0
|
LDIF
|
Distance of lightly-doped region
from heavily-doped region to transistor edge
|
Meter
|
0.0
|
MJ
|
Grading coefficient for gate-drain
and gate-source diodes
|
None
|
0.50
|
N
|
Emission coefficient for gate-drain
and gate-source diodes
|
None
|
1.0
|
NG
|
Gate subthreshold factor
|
Volt-1
|
0.0
|
NLEV
|
Noise equation selector
|
None
|
2
|
PB
|
Gate junction potential
|
Volt
|
0.8
|
RD
|
Drain ohmic resistance
|
Ohm
|
0.0
|
RG (RG2)
|
Gate ohmic resistance
|
Ohm
|
0.0
|
RS
|
Source ohmic resistance
|
Ohm
|
0.0
|
RSH
|
Sheet resistance of heavily-doped
region
|
Ohm/square
|
0.0
|
RSHG
|
Gate sheet resistance
|
Ohm/square
|
0.0
|
RSHL
|
Sheet resistance of lightly-doped
region
|
Ohm/square
|
0.0
|
TCV (VTOTC,
AVT0)
|
Temperature compensation coefficient
for threshold voltage VTO
|
°K-1
|
0.0
|
TLEV
|
Temperature equation selector for
junction diodes
|
None
|
0.0
|
TLEVC
|
Temperature equation selector for
junction capacitances and potential
|
None
|
0.0
|
TNOM (TREF)
|
Nominal circuit temperature
|
°C
|
25.0
|
TPB
|
Temperature coefficient for gate
junction potential PB
|
Volt/°K
|
0.0
|
TRD (TRD1,
ARD)
|
Temperature coefficient for drain
resistance RD
|
°K-1
|
0.0
|
TRG (TRG1,
ARG)
|
Temperature coefficient for gate
resistance RG
|
°K-1
|
0.0
|
TRS (TRS1,
ARS)
|
Temperature coefficient for source
resistance RS
|
°K-1
|
0.0
|
TT
|
Transit time
|
Second
|
0.0
|
VTO (VT0,
VPO)
|
Threshold voltage.
|
Volt
|
-2.0
|
W
|
FET gate width
|
Meter
|
0.0
|
WDEL
|
Difference between drawn width
and actual or optical device width
|
Meter
|
0.0
|
XTI
|
Saturation current temperature
exponent
|
None
|
3.0
|
SPICE JFET Model Netlist Example
J1 11 22 33 44 jfet1 AREA=0.97
.MODEL jfet1 NJF LEVEL=1
+ BETA=626e-6 LAMBDA=45e-3
+ VTO=-2.33 IS=0.5e-9
+ N=1.2 CGS=1e-15 CGD=1e-15
+ TT=1.0e-14 MJ=0.5 PB=0.7 FC=0.5
+ CAPOP=1
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