(M) MOSFET Statement
PLECS Spice supports a modified version of the standard Level 1 and Level 3 MOSFET model as well as a model for a vertically-diffused MOSFET (VDMOS).
Classic SPICE MOSFET models
The static equations for the supported LEVEL=1 and LEVEL=3 MOSFET models are identical to a larger extent to those of the original Spice3f5 models.
We have made minor modeling improvements to make the equations continuous, notably for the bulk junctions and for the evaluation of the threshold voltage.
Regarding the large-signal model, we do not support the Meyer model of the intrinsic charges because it does not conserve charge.
Instead, a simplified version of the BSIM3v3.3 charge model is implemented (capMod=2, 0/100 charge partition).
Mname drain gate source bulk modelName <<L>=l> <<W>=w> <AD=ad> <AS=as> <PD=pd> <PS=ps> <NRD=nrd> <NRS=nrs> <IC=vds,vgs,vbs> <TEMP=temp> <M=m>
.MODEL modelName NMOS <NAME=value ...>
Mname drain gate source <bulk> modelName <<L>=l> <<W>=w> <AD=ad> <AS=as> <PD=pd> <PS=ps> <NRD=nrd> <NRS=nrs> <off> <IC=vds,vgs,vbs> <TEMP=temp> <M=m>
.MODEL modelName NMOS <NAME=value ...>
When
bulkis omitted, it is assumed thatbulkis the same assource.During the operating point analysis, an initial guess for (\(V_\text{ds}\), \(V_\text{gs}\), \(V_\text{bs}\)) is chosen such that the MOSFET starts at the onset of conduction. When the
offflag is set, the initial voltage guesses are set to zero instead. Note that this option does not enforce a constraint on the solution found during the operating point analysis.
The MOSFET device type
NMOSorPMOSmust 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.
When importing a MOSFET model, the bulk node will be set equal to the source node
Instance Parameters
Parameter |
Description |
Default Value |
|---|---|---|
L |
Channel length |
\(10^{-4}\,\text{m}\) |
W |
Channel width |
\(10^{-4}\,\text{m}\) |
AD |
Drain diffusion area |
\(0\,\text{m}^2\) |
AS |
Source diffusion area |
\(0\,\text{m}^2\) |
PD |
Drain diffusion perimeter |
\(0\,\text{m}\) |
PS |
Source diffusion perimeter |
\(0\,\text{m}\) |
NRD |
Number of drain squares |
\(1\) |
NRS |
Number of source squares |
\(1\) |
IC |
Initial condition voltages (\(V_{\text{ds}}, V_{\text{gs}}, V_{\text{bs}}\)). |
none |
TEMP |
Device temperature |
\(27\,^\circ\text{C}\) |
M |
Number of parallel devices |
\(1\) |
When the
ICparameter is given, initial values for the drain-source (\(V_{\text{ds}}\)), the gate-source (\(V_{\text{gs}}\)), and bulk-source voltage (\(V_{\text{bs}}\)) must be specified.
Model Parameters
Parameter |
Description |
Default Value |
|---|---|---|
T_ABS |
Device temperature |
\(27\,^\circ\text{C}\) |
TNOM |
Nominal temperature |
\(27\,^\circ\text{C}\) |
LEVEL |
Specifies the level of the MOSFET model |
\(1\) |
VTO / VT0 |
Zero-bias threshold voltage |
\(0\,\text{V}\) |
PHI |
Surface-inversion potential |
\(0.6\,\text{V}\) |
KP |
Transconductance |
\(2\times 10^{-5}\,\text{A}/\text{V}^2\) |
GAMMA |
Bulk threshold parameter |
\(0\,\text{V}^{0.5}\) |
UO / U0 |
Surface mobility |
\(600\,\text{cm}^2/(\text{V}\text{s})\) |
NSS |
Surface state density |
\(0\,\text{cm}^{-2}\) |
NSUB |
Substrate doping |
\(0\,\text{cm}^{-3}\) |
TPG |
Type of the gate material |
\(1\) |
LD |
Lateral diffusion length |
\(0\,\text{m}\) |
TOX |
Gate insulation oxide thickness |
\(10^{-7}\,\text{m}\) |
CGSO |
Gate-source overlap capacitance per channel width |
\(0\,\text{F}/\text{m}\) |
CGDO |
Gate-drain overlap capacitance per channel width |
\(0\,\text{F}/\text{m}\) |
CGBO |
Gate-bulk overlap capacitance per channel length |
\(0\,\text{F}/\text{m}\) |
IS |
Reverse saturation current for the bulk-drain and bulk-source junctions |
\(10^{-14}\,\text{A}\) |
JS |
Reverse saturation current density for the bulk-drain and bulk-source junctions |
\(0\,\text{A}/\text{m}^2\) |
XTI |
Temperature exponent for IS and JS |
\(1\) |
N |
Emission coefficient for the bulk-drain and bulk-source junctions |
\(1\) |
PB |
Junction potential for the bulk-drain and bulk-source junctions |
\(0.75\,\text{V}\) |
MJ |
Grading coefficient for the bulk-drain and bulk-source junctions |
\(0.5\) |
CBD |
Bulk-drain zero-bias junction capacitance |
\(0\,\text{F}\) |
CBS |
Bulk-source zero-bias junction capacitance |
\(0\,\text{F}\) |
CJ |
Zero-bias junction capacitance per unit area |
\(0\,\text{F}/\text{m}^2\) |
MJSW |
Grading coefficient for the sidewall junction capacitance |
0.5 (LEVEL=1) 0.33 (LEVEL=3) |
CJSW |
Zero-bias sidewall junction capacitance |
\(0\,\text{F}/\text{m}\) |
FC |
Forward-bias depletion capacitance coefficient |
\(0.5\) |
TT |
Forward transit time for the bulk-drain and bulk-source junctions |
\(0\,\text{s}\) |
RSH |
Channel sheet resistance |
\(0\,\Omega\) |
RD |
Drain resistance |
NRD x RSH |
RS |
Source resistance |
NRS x RSH |
RG |
Gate resistance |
\(0\,\Omega\) |
RB |
Bulk resistance |
\(0\,\Omega\) |
RDS |
Drain-source resistance |
\(+\infty\,\Omega\) |
When
TPGit set to 1 (-1), it is assumed that the gate material has opposite (same) doping than the substrate. For an aluminum gate, setTPGto zero.You can specify the instance parameters
L,W,AD,AS,PD,PS,NRD, andNRSas model parameters too. If both are provided, the instance values take priority.The instance parameter
TEMPoverwrites the model parameterT_ABS.
Additional Parameters for the LEVEL=1 model
Parameter |
Description |
Default Value |
|---|---|---|
LAMBDA |
Channel length modulation |
\(0\,\text{V}^{-1}\) |
Additional Parameters for the LEVEL=3 model
Parameter |
Description |
Default Value |
|---|---|---|
DELTA |
Width effect on threshold voltage |
\(0\) |
ETA |
Static feedback on the threshold voltage |
\(1\) |
KAPPA |
Saturation field factor |
\(0.2\) |
NFS |
Fast surface state density |
\(0\,\text{cm}^{-2}\) |
THETA |
Mobility modulation |
\(0\,\text{V}^{-1}\) |
VMAX |
Maximum carrier drift velocity |
\(+\infty\,\text{m}/\text{s}\) |
XJ |
Metallurgical junction depth |
\(0\,\text{m}\) |
Note
We assume a different default value for VMAX than the original SPICE solvers. You can set VMAX=0 to reproduce the standard SPICE behavior.
VDMOS model
A simple model for a VDMOS, based on the static LEVEL=1 MOSFET equations and an explicitly modeled body diode, is supported.
While the gate-source capacitance is assumed constant, the gate-drain capacitance is modelled empirically using a nonlinear equation.
Mname drain gate source modelName <IC=vds,vgs> <TEMP=temp> <M=m>
.MODEL modelName VDMOS <nchan> <NAME=value ...>
Mname drain gate source source modelName <off> <IC=vds,vgs> <TEMP=temp> <M=m>
.MODEL modelName VDMOS <nchan> <NAME=value ...>
During the operating point analysis, an initial guess for (\(V_\text{ds}\), \(V_\text{gs}\)) is chosen such that the VDMOS starts at the onset of conduction. When the
offflag is set, the initial voltage guesses are set to zero instead. Note that this option does not enforce a constraint on the solution found during the operating point analysis.If a fourth terminal is given, it must coincide with the third terminal.
The VDMOS device type
VDMOSmust be specified in the model statement. The polarity of the device is set with thenchan(default) or thepchanflag.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 |
|---|---|---|
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
ICparameter is given, initial values for both the drain-source (\(V_{\text{ds}}\)), and the gate-source (\(V_{\text{gs}}\)) voltage must be specified.
Model Parameters
Parameter |
Description |
Default Value |
|---|---|---|
TNOM |
Nominal temperature |
\(27\,^\circ\text{C}\) |
VTO |
Zero-bias threshold voltage |
\(0\,\text{V}\) |
KP |
Transconductance |
\(1\,\text{A}/\text{V}^2\) |
LAMBDA |
Channel length modulation |
\(0\,\text{V}^{-1}\) |
MTRIODE |
Conductance multiplier in the linear regime |
\(1\) |
SUBSHIFT |
Shift in gate-source voltage of the subthreshold model |
\(0\,\text{V}\) |
KSUBTHRES |
Subthreshold parameter |
\(0.1\,\text{V}\) |
CGDMAX |
Maximum value of the gate-drain capacitance |
\(0\,\text{F}\) |
CGDMIN |
Minimum value of the gate-drain capacitance |
\(0\,\text{F}\) |
A |
Gate-drain capacitance parameter |
\(1\) |
CGS |
Gate-source capacitance |
\(0\,\text{F}\) |
RD |
Drain resistance |
\(0\,\Omega\) |
RS |
Source resistance |
\(0\,\Omega\) |
RG |
Gate resistance |
\(0\,\Omega\) |
RDS |
Drain-source resistance |
\(+\infty\,\Omega\) |
IS |
Reverse saturation current (body diode) |
\(10^{-14}\,\text{A}\) |
XTI |
Temperature exponent for IS (body diode) |
\(3\) |
EG |
Band gap energy (body diode) |
\(1.11\,\text{eV}\) |
N |
Emission coefficient (body diode) |
\(1\) |
BV |
Reverse breakdown voltage (body diode) |
\(\infty\,\text{V}\) |
IBV |
Reverse breakdown current (body diode) |
\(10^{-10}\,\text{A}\) |
NBV |
Emission coefficient for the reverse breakdown current (body diode) |
\(1\) |
VJ |
Junction potential (body diode) |
\(0.8\, \text{V}\) |
M |
Junction grading coefficient (body diode) |
\(0.5\) |
CJO |
Zero-bias junction capacitance (body diode) |
\(0\,\text{F}\) |
FC |
Forward-bias depletion capacitance coefficient (body diode) |
\(0.5\) |
TT |
Forward transit time (body diode) |
\(0\,\text{s}\) |
RB |
Series resistance (body diode) |
\(0\,\Omega\) |
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,Vds,Ron,Qg.
Examples
M1 d g s s nmosModel TEMP=125
.MODEL nmosModel NMOS LEVEL=1 VTO=3.5 KP=100 RD=0.05 RS=0.02 CGSO=1n CGDO=500p