User`s guide

B
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12 Conver
g
ence and “Time Step Too Small Errors”
Failure at the First Time Step
If the transient analysis fails at the first time point then usually
there is an unreasonably large capacitor or inductor. Usually
this is due to a typographical error. Consider the following
capacitor:
C 1 3, 0 1Ouf
“1O” (has the letter O) should have been “10.” This capacitor
has a value of one farad, not 10 microfarads. An easy way to
catch these is to use the LIST option (on the .OPTIONS
command).
LIST
The LIST option can echo back all the devices into the output
file that have their values in scientific notation.
That makes it easy to spot any unusual values. This kind of
problem does not show up during the bias point calculation
because capacitors and inductors do not participate in the bias
point.
Similar comments apply to the parasitic capacitance parameters
in transistor (and diode) models. These are normally echoed to
the output file (the NOMOD option suppresses the echo but the
default is to echo). As in the LIST output, the model parameters
are echoed in scientific notation making it easy to spot unusual
values. A further diagnostic is to ask for the detailed operating
bias point (.TRAN/OP) information.
.TRAN/OP
This lists the small-signal parameters for each semiconductor
device including the calculated parasitic capacitances.