MOSFETs

- General Form:
`m`*name**nd ng ns nb modname*[*parameters*...]

Parameter Name |
Description |
---|---|

off |
Device is initially nonconducting, for circuit convergence assistance. |

m=val |
Device multiplicity factor. |

l=val |
Channel length in meters. |

w=val |
Channel width in meters. |

ad=val |
Drain diffusion area in square meters. |

as=val |
Source diffusion area in square meters. |

pd=val |
Drain junction perimeter in meters. |

ps=val |
Source junction perimeter in meters. |

nrd=val |
Drain equivalent squares for resistance. |

nrs=val |
Source equivalent squares for resistance. |

ic=vds,vgs,vbs |
The initial voltages (initial condition) for transient analysis. |

icvds=vds |
The initial vds (initial condition) for
transient analysis. |

icvgs=vgs |
The initial vgs (initial condition) for
transient analysis. |

icvbs=vbs |
The initial vbs (initial condition) for
transient analysis. |

temp=val |
Device operating temperature, degrees celsius. |

- Examples:
`m1 24 2 0 20 type1`

m31 2 17 6 10 modm l=5u w=2u

m1 2 9 3 0 mod1 l=10u w=5u ad=100p as=100p pd=40u ps=40u

The parameters listed above are representative of the SPICE3 MOS
models, but except for ``m`' are fairly universal. Some
third-party MOS models may have additional nodes and parameters.
Consult the model documentation for the full listing.

The *nd*, *ng*, *ns*, and *nb* are the drain,
gate, source, and bulk (substrate) nodes, respectively. The *modname* is the model name, `l` and `w` specify the
channel length and width in meters, and `ad` and `as`
specify the areas of the drain and source diffusions in sq-meters.
Note that the suffix `u' specifies microns (1E-6 m) and `p'
sq-microns (1E-12 sq-m). If any of `l`, `w`, `ad`, or
`as` are not specified, default values are used. The use of
defaults simplifies input file preparation, as well as the editing
required if device geometries are to be changed. The `pd` and
`ps` specify the perimeters of the drain and source junctions in
meters, `nrd` and `nrs` designate the equivalent number of
squares of the drain and source diffusions; these values multiply
the sheet resistance `rsh` specified on the `.model` line
for an accurate representation of the parasitic series drain and
source resistance of each transistor. The `pd` and `ps`
default to 0.0 while `nrd` and `nrs` default to 1.0. The
parameter `off` indicates an initial condition of the device for
dc analysis. The initial conditions specified using `ic` or
alternatively `icvds`, `icvgs` amd `icvbs` are intended
for use with the `uic` option in transient analysis, when a
transient analysis is desired starting from other than the quiescent
operating point. operating point. The `.ic` line provides
another way to set initial conditions.

MOS devices using model levels 1-3 accept a real parameter ```m`''
which scales all the instance capacitances, areas, and currents by the
given `factor`. This can be used as a short-cut for modeling
multiple devices, e.g., `m = 2` is equivalent to two identical
devices in parallel. This is not available for most of the more
complicated and third-party models.