On Aug 2, 2009, at 12:24 PM, Mike Kordosky wrote: > > Hi, > I'm learning to use ngspice and gschem via the excellent tutorial > [1]http://geda.seul.org/wiki/geda:ngspice_and_gschem > I think there are a few small problems which if fixed would make > the > tutorial even better. I am not sure if this is the relevant mailing > list, I thought about geda-bug, but my problems are not software > bugs. > Anyway, please advise if this is not the right list. > Issues: > * I'm using gschem 1.4.3.20081231 and ngspice v19 on Ubuntu > 9.04. I > compiled ngspice from source but the gEDA suite came as a > collection > of ubuntu packages. > * I followed the tutorial all the way through and ran ngspice > but got > the following message: > Supplies reduced to 0.1000% Warning: singular matrix: check > nodes > 2n3904 and 2n3904 > ** Most users will know this output indicates a problem. But, it > would > be nice to point users to a sample file showing correct output. > ** I'd be surprised if this isn't a fairly well known problem. I > found a hint via google. My solution was to edit > Q1 1 Vbase 2 2N3904 > to > Q1 1 Vbase 2 0 2N3904 > I think the leading 2 in 2N3904 is being interpreted as a node > number > (for the substrate) by ngspice.
Yep. Ancient problem inherited from Berkeley. > The naive user needs to be helped > through this, Indeed. Old SPICE codgers recognize this problem, but it's hard to find an explanation. > perhaps by modifying 2N3904 to Q2N3904 in the text or > just by suggesting the hand edit. > * It would be helpful if the reader could download a correct > copy of > the netlist to compare with theirs. > * It would be helpful to "close the loop" and get the user to > graphical output, also introducing them to ngspice in interactive > mode. I'm suggesting: > ngspice [2]spice.net > ngspice 1 -> ac dec 20 1 100Meg > ngspice 2 -> plot vout vin vbase > which produces the attached plot for me. > Mike Kordosky > > References > > 1. http://geda.seul.org/wiki/geda:ngspice_and_gschem > 2. http://spice.net/<output.png> Why don't you ask Ales for access to the wiki? Go ahead and fix it. That's how we make progress. John Doty Noqsi Aerospace, Ltd. http://www.noqsi.com/ [email protected] _______________________________________________ geda-user mailing list [email protected] http://www.seul.org/cgi-bin/mailman/listinfo/geda-user
