On Sunday 26 May 2013, Orestes Mas wrote: > I must confess I'm a bit lost here, due to the fact I'm not > aware of some simulator internals.
One practical use of UIC is for circuits that have several metastable states, preventing convergence. > I know that to do transient simulations one must use > transient sources, perhaps a PWL 0,0 1n,8 in this case. But > the students tend to use DC source + UIC to simulate step > responses as they seems to consider this way "conceptually > easier". This problem arose when I was reviewing a student's > exercise where she printed out the current through the DC > source along with the inductor's current. A PWL is a correct way to do it. UIC is not. Especially in teaching. "At T=0, close the switch ...". To properly simulate, you need to do exactly that. > I simply used UIC because I wanted to start with zero current > in the inductor. If I don't do that the simulator > calculates the DC operating point on its own and The purpose of UIC is to prevent the simulator from calculating a DC operating point. To both specify an initial condition AND calculate the DC operating point is inconsistent, unless UIC were defined differently, such as to substitute a voltage source for the capacitor then calculate. Even that is not real, in the sense that real circuits don't do that. > > But wait... Are you meaning that if one wants to do a > transient simulation should use only transient sources? > perhaps a PWL 0,0 1n,8 in this case? yes. That one says that it starts at 0, then ramps up to 8 at 1 ns. In addition to showing the state change that starts the charging, it also shows that the voltage cannot change instantaneously. _______________________________________________ Help-gnucap mailing list [email protected] https://lists.gnu.org/mailman/listinfo/help-gnucap
