Component Statements

This device is supported within altergroups.

There are some convergence problems with this model because of Cgs going to zero beyond pinch off. The problems occur when the gate is driven from an inductive source, and there is no other capacitance at the gate. To prevent these problems, avoid setting Cgd to zero and add side wall capacitance to the gate-source and gate-drain junctions. A good estimate for these capacitors is C = pi*epsilon*w/2 where w is the gate width in microns and epsilon = 0.116 fF/micron.

Instance

Sample Instance Statement

m1 (1 2 0) nmes area=1 m=2

Instance Syntax

Name  d  g  s ModelName parameter=value ...

Instance Parameters

`area=1`	Junction area factor.
`m=1`	Multiplicity factor.
`trise`	Temperature rise from ambient.
`isnoisy=yes`	Should the device generate noise? Possible values are `no` or `yes`.
`region=fwd`	Estimated operating region. Spectre generates output number (0-4) in a rawfile. Possible values are `off`, `triode`, `sat`, `subth`, or `breakdown`.

Model Syntax

model modelName gaas parameter=value ...

Sample Model Statement

model nmes gaas type=n vto=-2 beta=0.06 lambda=0 b=0.25 rs=3.65 alpha=1.9 rd=1.98 is=1.1e-9 n=1.28 fc=0.5 cgs=0.365e-12

Model Parameters

Device type parameters

type=n

Transistor type. Possible values are n or p.

Drain current parameters

`vto=-2 V`	Pinch off voltage.
`beta=0.0001 A/V`²	Transconductance parameter.
`lambda=0 1/V`	Channel length modulation parameter.
`b=0.3 1/V`	Doping tail extending parameter.
`alpha=2 1/V`	Saturation voltage parameter.

Parasitic resistance parameters

`rd=0` Ω	Drain resistance (/area).
`rs=0` Ω	Source resistance (/area).
`rg=0` Ω	Gate resistance (/area).
`minr=0.1` Ω	Minimum source/drain/gate resistance.

Junction diode model parameters

`is=1e-14 A`	Gate saturation current (*area).
`n=1`	Emission coefficient for the gate junction.
imelt=`imax' A	Explosion current (*area).
`dskip=yes`	Use simple piecewise linear model for diode currents below 0.1*`iabstol`. Possible values are `yes` and `no`.

Junction capacitance model parameters

`capmod=2`	Charge model selector.
`cgs=0 F`	Gate-source zero-bias junction capacitance (*area).
`cgd=0 F`	Gate-drain zero-bias junction capacitance (*area).
`pb=1 V`	Gate junction potential.
`fc=0.5`	Junction capacitor forward-bias threshold.
`delta=0.2 V`	Gate capacitance pinch-off transition width.

Temperature effects parameters

21	`tnom (C)`	Parameters measurement temperature. Default set by options.
22	`trise=0 C`	Temperature rise from ambient.
23	`xti=3`	Temperature exponent for effect on `is`.

Operating region warning control parameters

`alarm=none`	Forbidden operating region. Possible values are `none`, `off`, `triode`, `sat`, `subth`, or `rev`.
`imax=1 A`	Maximum allowable current (*area).
`bvj=`∞ `V`	Junction reverse breakdown voltage.

Noise model parameters

`kf=0`	Flicker noise (1/f) coefficient.
`af=1`	Flicker noise (1/f) exponent.

Imax and Imelt:

---------------

The imax parameter aids in convergence and prevents numerical overflow. The junction characteristics of the device are accurately modeled for the value of the current up to imax. If the value of imax exceeds during iterations, the linear model is substituted until the current drops below imax or until convergence is achieved. If convergence is achieved with the current exceeding imax, the results are inaccurate, and Spectre prints a warning.

A separate model parameter, imelt, is used as a limit warning for the junction current. This parameter can be set to the maximum current rating of the device. When any component of the junction current exceeds imelt, given that base and collector currents are composed of many exponential terms, the results become inaccurate and Spectre issues a warning. The junction current is linearized above the value of imelt to prevent arithmetic exception, with the exponential term replaced by a linear equation at imelt.

The bv parameter detects the junction breakdown only. The breakdown currents of the junctions are not modeled.

Operating-Point Parameters

`type=n`	Transistor type. Possible values are `n` or `p`.
`region=fwd`	Estimated operating region. Spectre generates output number (0-4) in a rawfile. Possible values are `off`, `triode`, `sat`, `subth`, or `breakdown`.
`ids (A)`	Resistive drain current.
`vth (V)`	Threshold voltage.
`vgs (V)`	Gate-source voltage.
`vds (V)`	Drain-source voltage.
`vdsat (V)`	Drain saturation voltage.
`gm (S)`	Common-source transconductance.
`gds (S)`	Common-source output conductance.
`cgs (F)`	Gate-source capacitance.
`cgd (F)`	Gate-drain capacitance.
`ig (A)`	Resistive gate current.
`pwr (W)`	Power at operating point.
`meff`	Effective multiplicity factor (m-factor).

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