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.ic Line

General Form:
.ic v(nodname)=val | nodename=val ...
Example:
.ic v(11)=5 4=-5 v(2)=2.2

This line is for setting transient initial conditions. Note that the ``v( )'' around the node name is optional. It has two different interpretations, depending on whether the uic parameter is specified on the .tran line. Also, one should not confuse this line with the .nodeset line. The .nodeset line is only to help dc convergence, and does not affect final bias solution (except for multi-stable circuits). The two interpretations of this line are as follows:

  1. When the uic parameter is specified on the .tran line, then the node voltages specified on the .ic line are used to compute the capacitor, diode, BJT, JFET, and MOSFET initial conditions. This is equivalent to specifying the ic=... parameter on each device line, but is much more convenient. The ic=... parameter can still be specified and will take precedence over the .ic values. Since no dc bias (initial transient) solution is computed before the transient analysis, one should take care to specify all dc source voltages on the .ic line if they are to be used to compute device initial conditions.

  2. When the uic parameter is not specified on the .tran line, the dc bias (initial transient) solution will be computed before the transient analysis. In this case, the node voltages specified on the .ic line will be forced to the desired initial values during the bias solution. During transient analysis, the constraint on these node voltages is removed.


next up previous contents index
Next: .nodeset Line Up: Initialization Previous: .global Line   Contents   Index
Stephen R. Whiteley 2017-10-02