From: roucaries bastien <roucaries.bastien+qucs@gm...>  20130719 11:19:20

Le 18 juil. 2013 18:46, "Soeren D. Schulze" <soeren.d.schulze@...> a écrit : > > Am 18.07.2013 11:30, schrieb roucaries bastien: > >>> On a computer with finite precision, however, it's not advisable to follow >>> the electrical intuition too naively, because replacing a capacitor by DC >>> components and then doing a DC simulation in each step equals "factoring out >>> the Jacobian", which I mentioned above. >>> >>> I'm afraid I'm not that familiar with the code of other "realworld" >>> simulators. Do you know if they use the same approach? >> >> It is call companion model as norton form. It is uselly used as thevenin > > > Thanks. I checked gnucap, which does the same thing, and if I can trust some random web articles, Spice does it, too. I haven't used Spice that much, but convergence seems to be a bit better there, which I now can't explain any more. > > This is a bit surprising to me. For my Bachelor's thesis, I had primarily looked at mathematical literature on this topic, and they all write down the equation globally and then apply some standard solver, avoiding the condition problem. > > Apparently, electronic engineers and mathematicians don't talk to each other enough... They talk but only a few of them. Notice that the theory behind differential equation is hard. And notice that simulation is often need on crappy case : resonance is often a good case (in mathematical language source term is an eigenvalue/vector). Companion model help in this case by being equivalent to a pertubative method of first order (physician hat look like). Other case are resolved by hand by asymptotic method > > Sören 