Time-domain LRC circuit gives wrong amplitude (bug?)

I simulated a simple LRC series circuit combination here, where a trivial analytic result exists (long-time output sinoidal with 20 V amplitude). Frequency domain solution makes sense (~ 26 dBV on resonance), but when I drive it on resonance (15.85 kHz) the time-domain amplitude is only a bit over 6V. It should be 20V (out of paranoia, I checked this on [other software - edited by moderator], and indeed I get 20V amplitude, as expected from the analytic solution).

I'm using Chrome on Windows 10

Help would be most welcome--I'm relatively new to circuitlab, so I may be using it wrong somehow.

by karlberggren
November 30, 2016

Hi @karlberggren, this is just a numerical integration issue; the selected time step is affecting the amplitude of the result. Without changing your schematic at all, I just changed time step to be 0.01u (was 1u) and found that I get almost 20V amplitude.

By default, if the time step is too large, the numerical integration will tend to be "more stable" which tends to diminish ringing and oscillations. Hope that helps!

by mrobbins
December 01, 2016

OK, thanks, I should have checked that! I was really puzzled...

by karlberggren
December 02, 2016

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