9.1 Simulator Variables (.OPTIONS)
Various parameters of the simulations available in Ngspice 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 NGSPICE 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.
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 value for MOS drain diffusion area; the default is 0.0.
DEFAS=x
-
resets the value for MOS source diffusion area; the default is 0.0.
DEFL=x
-
resets the value for MOS channel length; the default is 100.0
micrometer.
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 Ngspice).
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 Ngspice).
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
-
sets the numerical integration method used by NGSPICE. 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 NGSPICE 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:
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.