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Measurements >> Other Measurements >> transient analysis
https://designers-guide.org/forum/YaBB.pl?num=1186681482

Message started by babunp114525 on Aug 9^th, 2007, 10:44am

Title: transient analysis
Post by babunp114525 on Aug 9^th, 2007, 10:44am

it is always advisable that if there is many non-linear components and clock in the circuit, then do the transient analysis as transient analysis may not give the stable operating point solution. Therefore, there may be convergence issue. Now, while doing the transient analysis, intitally the tool does the DC analysis prior to the transient analysis.

Then how is it possible for the tool to find out a converge point in the transient analysis (in the DC analysis which precedes the transient analysis), if it is not possible while doing the DC analysis? That is, how the transient analysis is done if the DC analysis fails as the transient analysis is dependent on the DC analysis?

Title: Re: transient analysis
Post by Geoffrey_Coram on Mar 19^th, 2008, 8:09am

When you say "Dc analysis fails" it could be that only DC Newton failed, and some pseudo-transient method succeeded (where p-t starts at an "easy" solution, like zero voltages, zero currents).

It's also possible (and some "fast spice" simulators are known to do this) to just start the transient without a known dc operating point. Any vector of voltages (and branch currents) can be used, and the simulator just proceeds. Consider if you stopped the transient in the middle of a simulation, then took that operating point as the starting point for a new transient. You have to start up with Backward-Euler so your integration formula doesn't need more data, but there's no requirement that the operating point be a dc solution.