Syntax: .savebias <filename> [internal]
+ [temp=<value>] [time=<value> [repeat]] [step=<value>]
+ [DC1=<value>] [DC2=<value>] [DC3=<value>]
This command writes a text file to disk that is reloaded with a .loadbias command in a subsequent simulation. If you have a circuit that has a difficult-to-solve DC operating point, you can save that solution to disk so that the next analysis can save time finding the DC solution before proceeding to the rest of the simulation.
The keyword "internal" can be added to indicate that the internal nodes of some devices should also be kept so that a more complete version of the DC solution is kept.
If you want to save a particular DC operating point from a .tran analysis, you can give specify a time. The first solved time point after the stipulated time will be written. The modifier "repeat" will cause the DC solution to be written after every period specified by this time. The file will contain only the most recently solved DC point. DC1, DC2, and DC3 can be given to extract a single operating point from .dc sweep analysis.
The savebias command writes a text file in the form of a .nodeset command. Note that nodeset statements are only recommendations of the solution. That is, the solver will start iterating the solution with the node voltages given in the nodeset statements, but will continue iterating until it's satisfied that the solution is valid. If you want to restart a .tran solution from the DC operating point, you can edit the file from a .nodeset to a .ic to try to coercive the solver to start from this DC state.
Since the integration state of all the circuit reactances isn't saved in the .savebias file, success with this technique varies.