JFETIDG Model (jfetidg)

JFETIDG is a compact model for four-terminal (that is, independent dual-gate) JFETs that is applicable to all regions of operation. It can also be applied to:

resistors (diffused or polysilicon) with a metal shield
the drift region of LDMOS transistors
the collector resistance of four-terminal vertical BJTs
junctionless MOS transistors

A cross-section of an n-channel device that can be modeled by JFETIDG is shown below (the thicker dashed lines represent the edges of the depletion regions in the channel region, from both the bottom and top gates; the metallurgical thickness of the channel is tm).

JFETIDG uses a unified, physical formulation for depletion pinching of the conducting channel that is applicable to both pn-junction gates and MOS gates, and independent of gate type (apart from how the JFETIDG model parameters are computed from physical parameters). JFETIDG uses an exact solution for depletion pinching modulation of the channel current Ids, which is more accurate than linearizing with respect to the mid-point-potential. JFETIDG also models:

self-heating
velocity saturation (inherited from the r3 model)
channel length modulation (CLM)
drain-induced barrier lowering (DIBL)
impact ionization (i.e. weak avalanche)
mobility modulation, by both bottom and top gate biases
parasitic pn-junction leakage current
parasitic pn-junction breakdown current
depletion and diffusion capacitance for pn-junction gates
fixed capacitance for MOS gates
selectable local (single geometry) and global (geometry dependent) models
channel conductance and depletion modulation parameters can either be specified directly or calculated from physical doping and layer thickness values
temperature dependence
noise, including from parasitic pn-junction currents
statistical variations

The large-signal equivalent circuit for JFETIDG is shown below.

The power generated by the electrical part of JFETIDG (the left side of the network above), Ith, drives the thermal part of JFETIDG (the right side of the network above), and the behavior of the electrical part depends on the local temperature rise, Temp(dt), generated by the thermal part. The electrical and thermal parts are solved self-consistently. The parasitic capacitances include both linear components (for MOS gates) and non-linear components (for pn-junction gates); The parasitic currents include pn-junction, breakdown, and impact ionization components; these are only applicable to pn-junction gates so are turned off for MOS gates.

Terminology and Notation

non-pinch-off	operation when neither end of a device is pinched off (analogous to MOSFET strong inversion non-saturation)
drain pinch-off	operation when one end of a device is pinched off (analogous to MOSFET strong inversion saturation)
source pinch-off	operation when both ends of a device are pinched off (analogous to MOSFET weak inversion)
Vds	voltage across the intrinsic body portion of the device `V(di)-V(si)`
Ids	current through the intrinsic body portion of the device (see equivalent circuit below)
Vgbs	bottom-gate to intrinsic source voltage `V(gb)-V(si)`
Vgbd	bottom-gate to intrinsic drain voltage `V(gb)-V(di)`
Vgts	top-gate to intrinsic source voltage `V(gt)-V(si)`
Vgtd	top-gate to intrinsic drain voltage `V(gt)-V(di)`
[sd]	applies for both source and drain
[bt]	applies for both bottom and top gate
[ap]	applies for both area and perimeter components
[2]	also applies to an optional second perimeter component

Parameters and nodes are set in Courier New font. k is Boltzmann's constant, q is the magnitude of the electronic charge, and ni is the intrinsic carrier concentration. The thermal voltage is t=kT/q where T is the device temperature in K. Si and ox are the permittivities of silicon and silicon dioxide, respectively.

For convenience, and to be able to help debug circuit problems and understand what is the dominant source of nonlinearity, the physical effects can be turned off individually.

setting swlin to 1 turns off all nonlinearities
setting swet to 0 turns off self-heating
setting the thermal conductance gth to 0 when the local termperature rise port dt is not connected turns off self-heating
setting ecrit to be >=109 V/m turns off modeling of velocity saturation (the breakdown field for silicon is about 3×107 V/m)
setting dfbfac to 0 turns off modeling of depletion pinching by the bottom gate
setting dftfac to 0 turns off modeling of depletion pinching by the top gate

Any combination of sources of nonlinearity can be switched off by appropriate specification of these parameters.

Model Version

SPECTRE supports JFETIDG model version 1.0.0.

Component Statements

This device is supported within altergroups.

Instance Syntax

Name ( d gb s gt [dt] ) ModelName <parameter=value> ...

Instance Parameters

`w=1e-06 m`	Design width of JFET body.
`l=1e-06 m`	Design length of JFET body.
`wd=0 m`	Dogbone width (total; not per side).
`asb=0 m^2`	Area of source to bottom gate.
`ast=0 m^2`	Area of source to top gate.
`psb=0 m`	Perimeter of source to bottom gate.
`psb2=0 m`	Perimeter of source to bottom gate (2nd component).
`pst=0 m`	Perimeter of source to top gate.
`pst2=0 m`	Perimeter of source to top gate (2nd component).
`cs=0`	Number of contacts at source end.
`adb=0 m^2`	Area of drain to bottom gate.
`adt=0 m^2`	Area of drain to top gate.
`pdb=0 m`	Perimeter of drain to bottom gate.
`pdb2=0 m`	Perimeter of drain to bottom gate (2nd component).
`pdt=0 m`	Perimeter of drain to top gate.
`pdt2=0 m`	Perimeter of drain to top gate (2nd component).
`cd=0`	Number of contacts at drain end.
`trise=0 degC`	Local temperature delta to ambient (before self-heating).
`dta=0 degC`	Local temperature delta to ambient (before self-heating).
`dtemp=0 degC`	Local temperature delta to ambient (before self-heating).
`nsmm_rsh=0`	Number of standard deviations of local variation for rsh.
`nsmm_w=0`	Number of standard deviations of local variation for w.
`nsmm_l=0`	Number of standard deviations of local variation for l.
`mult`=`1`	Multiplicity factor.
`swnoise=1`	Switch to include noise: 0=no and 1=yes.
`swet=1`	Switch to include self-heating: 0=no and 1=yes.
`swlin=0`	Switch to force linearity: 0=no and 1=yes.
`swmman`	Switch to enable mismatch analysis: 0=no and 1=yes.
`m=1`	Alias of mult.

The switch parameters can also be specified as model parameters, and a value specified on an instance line overrides a value specified on a model card.

The following figure shows how the instance parameters should be determined for a typical JFET layout.

The end region dogbone may be asymmetric between the two sides.

The total width of the source end region is:

where the contact width, contact spacing, and contact-to-edge distances, wc, wc2c, and wc2e, respectively, are shown in the layout.

If cs is zero (which happens for non-end sections of a multi-section model) then as[bt] and ps[bt] should be calculated as half of the area and length direction perimeter, respectively, of the body of the JFET (that is, 0.5·w·l and l, respectivey). If cs is greater than zero then the area and (non-body adjacent) perimeter of the left end region should be added to these values. Similarly for ad[bt] and pd[bt].

Model Syntax

model ModelName jfetidg <parameter=value> ...

Model Parameters

The naming convention for parameters follows the PSP style. Global model parameters append o, l, w, lw, and so on, to the name of the associated local geometry model parameter.

`level=1`	Model level.
`paramchk=0`	Model parameter checking selector.
`version=1`	Model version.
`subversion=0`	Model subversion.
`revision=2`	Model revision.
`tmin=100 degC`	Minimum ambient temperature.
`tmax=500 degC`	Maximum ambient temperature.
`gmin=1e-12 S`	Minimum parasitic conductance.
`imax=1 A`	Current at which to linearize diode currents.
`scale=1`	Scale factor for instance geometries.
`shrink=0 %`	Shrink percentage for instance geometries.
`rthresh=0.001 Ω`	Threshold to switch end resistance to V=I*R form.
`type=n`	JFET type: +1=n-body and -1=p-body. Possible values are `n` and `p`.
`swbgmos=0`	Switch to indicate bottom gate type: 0=pn-junction and 1=mos.
`swtgmos=0`	Switch to indicate top gate type: 0=pn-junction and 1=mos.
`swgeo=1`	Switch for geometry modeling: 0=local and 1=global.
`swgdep=1`	Switch for geometry mapping basis: 0=drawn and 1=effective.
`tnom=27 degC`	Nominal (reference) temperature.
`lmin=0.0 m`	Minimum allowed drawn length.
`lmax=9e+09 m`	Maximum allowed drawn length.
`wmin=0.0 m`	Minimum allowed drawn width.
`wmax=9.9e+09 m`	Maximum allowed drawn width.
`jmax=1e+08 A/m`	Maximum current density.
`vmax=9.9e09 V`	Maximum drain or source voltage w.r.t. either gate.
`tminclip=(-100) degC`
	Clip minimum temperature.
`tmaxclip=800 degC`	Clip maximum temperature.
`grpo=1e-12`	Minimum body conductance in pinch-off (ratio w.r.t. Vc=0).
`xw=0 m`	Width offset (total).
`nwxw=0 m`	Narrow width offset correction coefficient.
`wexw=0 m`	Webbing effect width offset correction coefficient (for dogboned devices).
`fdrwo=1e-06 m`	Finite doping width offset reference width.
`fdxwo=0 m`	Finite doping width offset width value for wide devices.
xl=0 m	Length offset (total).
xlw=0 m	Width dependence of length offset.
dxlsat=0 m	Additional length offset for velocity saturation calculation.
tm=5e-07 m	Channel thickness (metallurgical).
nc=1e+23 /m^3	Channel doping concentration.
nb=1e+22 /m^3	Bottom-gate doping concentration.
toxb=4e-07 m	Bottom-gate oxide thickness.
vfbb=0 V	Bottom-gate flatband voltage.
nt=1e+26 /m^3	Top-gate doping concentration.
toxt=4e-07 m	Top-gate xide thickness.
vfbt=0 V	Top-gate flatband voltage.
dfb=0.01 /V^0.5	Bottom-gate depletion factor (overrides calculation if specified).
dfbo=0.01 /V^0.5	`dfb` Geometry-independent part.
dfbl=0	`dfb 1/l` coefficient.
dfble=1	`dfb 1/l` exponent.
dfbw=0	`dfb 1/w` coefficient.
dfbwe=1	`dfb 1/w` exponent.
dfblw=0	`dfb 1/(l*w)` coefficient.
dfbfac=1	`dfb` adjustment coefficient.
psirb=2 V	Bottom-gate depletion potential (overrides calculation if specified).
psirbo=2 V	`psirb` Geometry-independent part.
psirbl=0	`psirb 1/l` coefficient.
psirble=1	`psirb 1/l` exponent.
psirbw=0	`psirb 1/w` coefficient.
psirbwe=1	`psirb 1/w` exponent.
psirblw=0	`psirb 1/(l*w)` coefficient.
psirbfac=1	`psirb` adjustment coefficient.
dft=0.01 /V^0.5	Top-gate depletion factor (overrides calculation if specified).
dfto=0.01 /V^0.5	`dft` Geometry-independent part.
dftl=0.0	`dft 1/l` coefficient.
dftle=1.0	`dft 1/l` exponent.
dftw=0.0	`dft 1/w` coefficient.
dftwe=1.0	`dft 1/w` exponent.
dftlw=0.0	`dft 1/(l*w)` coefficient.
dftfac=1.0	`dft` adjustment coefficient.
psirt=2.0 V	Top-gate depletion potential (overrides calculation if specified).
psirto=2.0 V	`psirt` Geometry-independent part.
psirtl=0.0	`psirt 1/l` coefficient.
psirtle=1.0	`psirt 1/l` exponent.
psirtw=0.0	`psirt 1/w` coefficient.
psirtwe=1.0	`psirt 1/w` exponent.
psirtlw=0.0	`psirt 1/(l*w)` coefficient.
psirtfac=1.0	`psirt` adjustment coefficient.
mu0=0.05 m^2/V/s	Low-field mobility
r0=100 Ohm	Zero-bias resistance.
rsh0=100 Ohm/sq	Zero-bias sheet resistance (overrides calculation if specified).
rzd=100 Ohm	Zero-depletion resistance.
rshzd=100 Ohm/sq	Zero-depletion sheet resistance (overrides calculation if specified).
rcs=0 Ohm	Source contact resistance.
rcd=0 Ohm	Drain contact resistance.
rc=0 Ohm	Resistance per contact.
rcw=0 Ohm	Width adjustment for contact resistance.
diblb=0	Bottom-gate `dibl`.
diblbl=0	`diblb l` dependence coefficient.
diblt=0	Top-gate `dibl`.
dibltl=0	`diblt l` dependence coefficient.
diblle=1	`dibl l` dependence exponent.
diblv=0.1 V	`dibl` voltage offset.
dible=0.5	`dibl` voltage exponent.
clm1=0	`clm` linear component.
clm1l=0	`clm1 l` dependence coefficient.
clm1le=1	`clm1 l` dependence exponent.
clm1c=0 /V	`clm1 V(gx)` dependence coefficient.
clm2=0	`clm` nonlinear component.
clm2l=0	`clm2 l` dependence coefficient.
clm2le=1	`clm2 l` dependence exponent.
clm2v=0.1 V	`clm2` voltage offset.
clm2e=0.5	`clm2` voltage exponent.
ats=0.0 V	Saturation smoothing parameter.
atso=0 V	`ats` Geometry-independent part.
atsl=0 V	`ats 1/l` coefficient.
axs=0	Second saturation smoothing parameter.
axso=0	`axs` Geometry-independent part.
axsl=0	`axs 1/l` coefficient.
nspo=1	Slope parameter under source pinch-off.
nspoo=1	`nspo` Geometry-independent part.
nspol=0	`nspo 1/l` coefficient.
nspole=1	`nspo 1/l` exponent.
nspow=0	`nspo 1/w` coefficient.
nspowe=1	`nspo 1/w` exponent.
nspolw=0	`nspo 1/(l*w)` coefficient.
alphab=0 /V	Bottom-gate impact ionization current prefactor.
alphabo=0 /V	`alphab` Geometry-independent part.
alphabl=0 /V	`alphab 1/l` coefficient.
alphat=0 /V	Top-gate impact ionization current prefactor.
alphato=0 /V	`alphat` Geometry-independent part.
alphatl=0 /V	`alphat 1/l` coefficient.
beta=10 V	Impact ionization current exponent for both gates.
mumb=0 /V	Bottom-gate mobility modulation coefficient.
mumboff=0 V	Bottom-gate mobility modulation voltage offset.
mumbs=1	Bottom-gate mobility modulation smoothing parameter.
mumbe=1	Bottom-gate mobility modulation exponent.
mumbo=0 /V	`mumb` Geometry-independent part.
mumbl=0	`mumb 1/l` coefficient.
mumbw=0	`mumb 1/w` coefficient.
mumblw=0	`mumb 1/(l*w)` coefficient.
mumt=0 /V	Top-gate mobility modulation coefficient.
mumtoff=0 V	Top-gate mobility modulation voltage offset.
mumts=1	Top-gate mobility modulation smoothing parameter.
mumte=1	Top-gate mobility modulation exponent.
mumto=0 /V	`mumt` Geometry-independent part.
mumtl=0	`mumt 1/l` coefficient.
mumtw=0	`mumt 1/w` coefficient.
mumtlw=0	`mumt 1/(l*w)` coefficient.
mumii1=0 /V^2	Linear impact ionization mobility modulation coefficient.
mumii2=0 /V^4	Quadratic impact ionization mobility modulation coefficient.
vcrit=4 V	Velocity saturation critical voltage.
ecrit=4e+06 V/m	Velocity saturation critical field.
vcorn=0.4 V	Velocity saturation corner voltage.
ecorn=4e+05 V/m	Velocity saturation corner field.
du=0.02	Mobility reduction at ecorn.
voffspo=0	Source pinchoff offset (number of `nspo*phi_t`).
moffspo=1	Source pinchoff smoothing factor.
gth=0 W/K	Thermal conductance.
`gtho=0 W/K`	`gth` Geometry-independent part.
`gthp=0 W/K/m`	`gth` perimeter component.
`gtha=0 W/K/m`²	`gth` area component.
`gthc=0 W/K`	`gth` contact component.
`cth=0 s W/K`	Thermal capacitance.
`ctho=0 s W/K`	`cth` Geometry-independent part.
`cthp=0 s W/K/m`	`cth` perimeter component.
`ctha=0 s W/K/m`²	`cth` area component.
`cthc=0 s W/K`	cth contact component.
`fc=0.9`	Ddepletion capacitance linearization factor.
`isab=0 A/m`²	Bottom-gate diode saturation current per unit area.
`nab=1`	Bottom-gate ideality factor for `isa`.
`cab=0 F/m`²	Bottom-gate fixed capacitance per unit area.
`cjab=0 F/m`²	Bottom-gate depletion capacitance per unit area.
`pab=0.75 V`	Bottom-gate built-in potential for cja.
`mab=0.33`	Bottom-gate grading coefficient for cja.
`ajab=-0.5 V`	Bottom-gate smoothing parameter for cja.
`ispb=0 A/m`	Bottom-gate diode saturation current per unit perimeter.
`npb=1`	Bottom-gate ideality factor for isp.
`cpb=0 F/m`	Bottom-gate fixed capacitance per unit perimeter.
`cpb2=0 F/m`	Bottom-gate fixed capacitance per unit perimeter (2nd component).
`cjpb=0 F/m`	Bottom-gate depletion capacitance per unit perimeter.
`ppb=0.75 V`	Bottom-gate built-in potential for cjp.
`mpb=0.33`	Bottom-gate grading coefficient for cjp.
`ajpb=-0.5 V`	Bottom-gate smoothing parameter for cjp.
`ttb=0 s`	Bottom-gate transit time for diffusion charge.
`vbvb=0 V`	Bottom-gate breakdown voltage.
`nbvb=1`	Bottom-gate ideality factor for breakdown current.
`isat=0 A/m`²	Top-gate diode saturation current per unit area.
`nat=1`	Top-gate ideality factor for isa.
`cat=0 F/m`²	Top-gate fixed capacitance per unit area.
`cjat=0 F/m`²	Top-gate depletion capacitance per unit area.
`pat=0.75 V`	Top-gate built-in potential for cja.
`mat=0.33`	Top-gate grading coefficient for cja.
`ajat=-0.5 V`	Top-gate smoothing parameter for cja.
`ispt=0 A/m`	Top-gate diode saturation current per unit perimeter.
`npt=1`	Top-gate ideality factor for isp.
`cpt=0 F/m`	Top-gate fixed capacitance per unit perimeter.
`cpt2=0 F/m`	Top-gate fixed capacitance per unit perimeter (2nd component).
`cjpt=0 F/m`	Top-gate depletion capacitance per unit perimeter.
`ppt=0.75 V`	Top-gate built-in potential for cjp.
`mpt=0.33`	Top-gate grading coefficient for cjp.
`ajpt=-0.5 V`	Top-gate smoothing parameter for cjp.
`ttt=0 s`	Top-gate transit time for diffusion charge.
`vbvt=0 V`	Top-gate breakdown voltage.
`nbvt=1`	Top-gate ideality factor for breakdown current.
`ibv=1e-06 A`	Current at breakdown.
`kfn=0 m`²	Flicker noise coefficient.
`afn=2`	Flicker noise current exponent.
`bfn=1`	Flicker noise 1/f exponent.
`swfngeo=0`	Switch for flicker noise geometry calculation: 0=drawn and 1=effective.
`tc1psirb=0 /K`	`psirb` linear TC.
`tc2psirb=0 /K`²	`psirb` quadratic TC.
`tc1psirt=0 /K`	`psirt` linear TC.
`tc2psirt=0 /K`²	`psirt` quadratic TC.
`tc1=0 /K`	Resistance linear TC.
`tc2=0 /K`²	Resistance quadratic TC.
`tc1o=0 /K`	`tc1` Geometry-independent part.
`tc2o=0 /K`²	`tc2` Geometry-independent part.
`tc1w=0 m/K`	`tc1 1/w` coefficient.
`tc2w=0 m/K`²	`tc2 1/w` coefficient.
`tc1l=0 m/K`	`tc1 1/l` coefficient.
`tc2l=0 m/K`²	`tc2 1/l` coefficient.
`tc1lw=0 m`²`/K`	`tc1 1/(l*w)` coefficient.
`tc2lw=0 m`²`/K`²	`tc2 1/(l*w)` coefficient.
`tsl=0 /K`	Slope of resistance change compared to temperature at low temperature.
`tsh=0 /K`	Slope of resistance change compared to temperature at high temperature.
`tsct=100 degC`	Critical temperature where resistance change slope goes from tsl to tsh.
`tssm=10 degC`	Resistance change slope smoothing parameter.
`tslo=0 /K`	`tsl` Geometry-independent part.
`tsho=0 /K`	`tsh` Geometry-independent part.
`tscto=100 degC`	`tsct` Geometry-independent part.
`tssmo=10 degC`	`tssm` Geometry-independent part.
`tslw=0 m/K`	`tsl 1/w` coefficient.
`tshw=0 m/K`	`tsh 1/w` coefficient.
`tsctw=0 m degC`	`tsct 1/w` coefficient.
`tssmw=0 m degC`	`tssm 1/w` coefficient.
`tsll=0 m/K`	`tsl 1/l` coefficient.
`tshl=0 m/K`	`tsh 1/l` coefficient.
`tsctl=0 m degC`	`tsct 1/l` coefficient.
`tssml=0 m degC`	`tssm 1/l` coefficient.
`tsllw=0 m`²`/K`	`tsl 1/(l*w)` coefficient.
`tshlw=0 m`²`/K`	`tsh 1/(l*w)` coefficient.
`tsctlw=0 m`² `degC`	`tsct 1/(l*w)` coefficient.
`tssmlw=0 m`² `degC`	`tssm 1/(l*w)` coefficient.
`tc1rc=0 /K`	Contact resistance linear TC.
`tc2rc=0 /K`²	Contact resistance quadratic TC.
`xbeta=0`	Exponent for impact ionization current exponent temperature dependence.
`tegth=0`	Thermal conductance temperature exponent.
`xvsat=0`	Exponent for saturation velocity temperature dependence.
`xvsato=0`	`xvsat` Geometry-independent part.
`xvsatl=0`	`xvsat 1/l` coefficient.
`xvsatle=1`	`xvsat 1/l` exponent.
`ea=1.12 V`	Activation voltage for diode temperature dependence.
`xis=3`	Exponent for diode temperature dependence.
`tc1vbvb=0 /K`	Breakdown voltage linear TC (bottom gate).
`tc2vbvb=0 /K`²	Breakdown voltage quadratic TC (bottom gate).
`tc1nbvb=0 /K`	Breakdown ideality factor linear TC (bottom gate).
`tc1vbvt=0 /K`	Breakdown voltage linear TC (top gate).
`tc2vbvt=0 /K`²	Breakdown voltage quadratic TC (top gate).
`tc1nbvt=0 /K`	Breakdown ideality factor linear TC (top gate).
`tc1kfn=0 /K`	Flicker noise coefficient linear TC.
`nsig_rsh=0`	Number of standard deviations of global variation for `rsh`.
`nsig_w=0`	Number of standard deviations of global variation for `w`.
`nsig_l=0`	Number of standard deviations of global variation for `l`.
`sig_rsh=0 %`	Global variation standard deviation for `rsh` (relative).
`sig_w=0 m`	Global variation standard deviation for `w` (absolute).
`sig_l=0 m`	Global variation standard deviation for `l` (absolute).
`smm_rsh=0 %m`	Local variation standard deviation for `rsh` (relative).
`smm_w=0 m^1.5`	Local variation standard deviation for `w` (absolute).
`smm_l=0 m^1.5`	Local variation standard deviation for `l` (absolute).
`swmmgdep=0`	Switch for mismatch geometry calculation: 0=drawn and 1=effective.
`swnoise=1`	Switch to include noise: 0=no and 1=yes.
`swet=1`	Switch to include self-heating: 0=no and 1=yes.
`swlin=0`	Switch to force linearity: 0=no and 1=yes.
`swmman=0`	Switch to enable mismatch analysis: 0=no and 1=yes.
`tref (degC)`	Alias of tnom.
`tr (degC)`	Alias of tnom.
`compatible=spectre`	Encourage device equations to be compatible with a foreign simulator. Possible values are `spectre`, `spice2`, `spice3`, `cdsspice`, `spiceplus`, `eldo`, `sspice`, `mica`, and `pspice`.

Output Parameters

`tempeff (C)`
	Effective temperature for a single device.
`meff`	Effective multiplicity factor (m-factor).

Operating Point Parameters

`jtype`	JFET type: +1=n-body and -1=p-body.
`leff_m (m`	Effective electrical length.
`weff_m (m)`	Effective electrical width.
`rth (K/W)`	Thermal resistance at ambient temperature.
`cth_i (s W/K)`	Thermal capacitance.
`v (V)`	Voltage across JFET.
`ids (A)`	Current through JFET body.
`r_dc (`Ω`)`	DC resistance (including bias and temperature dependence).
`r_ac (`Ω`)`	AC resistance (including bias and temperature dependence).
`cgbs (F)`	Bottom-gate to source capacitance.
`cgbd (F)`	Bottom-gate to drain capacitance.
`cgts (F)`	Top-gate to source capacitance.
`cgtd (F)`	Top-gate to drain capacitance.
`vsp (V)`	Source voltage difference w.r.t. to pinch-off.
`vdsat (V)`	Drain-source saturation voltage.

Spectre Circuit Simulator Components and Device Models Reference
Product Version 23.1, June 2023