Simulator Variables

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Simulator Variables

SIMULATOR VARIABLES (.OPTIONS)

Various parameters of the simulations available in Spice3 can be altered to control the accuracy, speed, or default values for some devices. These parameters may be changed via the "set" command (described later in the section on the interactive front-end) or via the ".OPTIONS" line:

General form:

.OPTIONS OPT1 OPT2 ... (or OPT=OPTVAL ...)

Examples:

.OPTIONS RELTOL=.005 TRTOL=8

The options line allows the user to reset program control and user options for specific simulation purposes. Additional options for Nutmeg may be specified as well and take effect when Nutmeg reads the input file. Options specified to Nutmeg via the 'set' command are also passed on to SPICE3 as if specified on a .OPTIONS line. See the following section on the interactive command interpreter for the parameters which may be set with a .OPTIONS line and the format of the 'set' 'command. Any combination of the following options may be included, in any order. 'x' (below) represents some positive number.

Option

Effect

ABSTOL=x

resets the absolute current error tolerance of the program. The default value is 1 picoamp.

BADMOS3

Use the older version of the MOS3 model with the "kappa" discontinuity.

CHGTOL=x

resets the charge tolerance of the program. The default value is 1.0e-14.

DEFAD=x

resets the charge tolerance of the program. The default value is 1.0e-14.

DEFAS=x

resets the value for MOS source diffusion area; the default is 0.0.

DEFL=x

resets the value for MOS source diffusion area; the default is 0.0.

DEFW=x

resets the value for MOS channel width; the default is 100.0 micrometer

GMIN=x

resets the value of GMIN, the minimum conductance allowed by the program. The default value is 1.0e-12.

ITL1=x

resets the dc iteration limit. The default is 100.

ITL2=x

resets the dc transfer curve iteration limit. The default is 50.

ITL3=x

resets the lower transient analysis iteration limit. the default value is 4. (Note: not implemented in Spice3).

ITL4=x

resets the transient analysis timepoint iteration limit. the default is 10.

ITL5=x

resets the transient analysis total iteration limit. the default is 5000. Set ITL5=0 to omit this test. (Note: not implemented in Spice3).

KEEPOPINFO

Retain the operating point information when either an AC, Distortion, or Pole-Zero analysis is run. This is particularly useful if the circuit is large and you do not want to run a (redundant) ".OP" analysis.

METHOD=name

resets the numerical integration method used by SPICE. Possible names are "Gear" or "trapezoidal" (or just "trap"). The default is trapezoidal.

PIVREL=x

resets the relative ratio between the largest column entry and an acceptable pivot value. The default value is 1.0e-3. In the numerical pivoting algorithm the allowed minimum pivot value is determined by EPSREL=AMAX1(PIVREL*MAXVAL, PIVTOL) where MAXVAL is the maximum element in the column where a pivot is sought (partial pivoting).

PIVTOL=x

resets the absolute minimum value for a matrix entry to be accepted as a pivot. The default value is 1.0e-13.

RELTOL=x

resets the relative error tolerance of the program. The default value is 0.001 (0.1%).

TEMP=x

Resets the operating temperature of the circuit. The default value is 27 deg C (300 deg K). TEMP can be overridden by a temperature specification on any temperature dependent instance.

TNOM=x

resets the nominal temperature at which device parameters are measured. The default value is 27 deg C (300 deg K). TNOM can be overridden by a specification on any temperature dependent device model.

TRTOL=x

resets the transient error tolerance. The default value is 7.0. This parameter is an estimate of the factor by which SPICE overestimates the actual truncation error.

TRYTOCOMPACT

Applicable only to the LTRA model. When specified, the simulator tries to condense LTRA transmission lines' past history of input voltages and currents.

VNTOL=x

resets the absolute voltage error tolerance of the program. The default value is 1 microvolt.

In addition, the following options have the listed effect when operating in spice2 emulation mode:

Option

Effect

ACCT

causes accounting and run time statistics to be printed

LIST

causes the summary listing of the input data to be printed

NOMOD

suppresses the printout of the model parameters

NOPAGE

suppresses page ejects

NODE

causes the printing of the node table.

OPTS

causes the option values to be printed.