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Initial conditions force a node to a fixed voltage or current during the calculation of the DC bias point. There are two types of initial condition namely soft and hard. Soft initial conditions apply a voltage through a fixed resistance. Hard initial conditions, apply a voltage directly without any resistance.
Soft initial conditions are implemented using the .IC control and will also correctly apply an initial condition when Skip DC bias point is specified for a transient analysis. The driving resistance for a soft initial condition is 1 by default but can be altered using the ICRES simulator option. To do this, add .OPTIONS ICRES=nnn to the F11 window (see Manual Entry of Simulator Commands).
Hard Initial conditions are implemented using a voltage source with the DCOP parameter specified. This feature is proprietary to SIMetrix and is not compatible with other SPICE simulators. Refer to the Simulator Reference Manual/Analog Device Reference/Voltage Source for more information on voltage sources and the DCOP parameter.
Nodesets are used to help convergence and also to coerce a particular state for circuits that have more than one possible DC solution. More information about nodesets is given in the Simulator Reference Manual/Command Reference/.NODESET.
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