On Tue, Sep 14, 2010 at 1:55 AM, Brennan Ashton <[email protected]>wrote:
> On Mon, Sep 13, 2010 at 3:10 PM, Ashwith Rego <[email protected]> wrote: > > Hi > > I've just begun using ngspice and found that I cannot plot the current > > output. Also, I cannot specify the name of a circuit component in a > .PRINT > > or .PLOT statement. Only the node numbers seem to work. Here is an > example: > > Ohm' Law > > > > > ngspice doesn't seem to recognize R1 in the .PRINT statement. I get the > > following error: > > > > $ngspice -b diff.net > > > Warning: can't parse 'r1': ignored > > SPICE uses nodal analysis so it has the voltages at every node, it is > up to you to determine what the differential measurement will be, for > the voltage over the resistor you have to list the two nodes, 1 and 0. > This is all normal behavior. > > > > ------------------------------------------------------------------------------------------------- > > The simulation however works if I replace it with > > .PRINT DC V(0,1) > > > Secondly, I can't seem to print current. Using > > .PRINT DC I(R1) or .PRINT DC I(0,1) gives me this error: > > $ngspice -b diff.net > > > > Circuit: ohm's law > > > > Doing analysis at TEMP = 27.000000 and TNOM = 27.000000 > > > > Warning: can't parse '0#branch': ignored > > Error: no data saved for D.C. Transfer curve analysis; analysis not run > > doAnalyses: not found > > This is also normal, spice will only calculate the current though a > voltage source. The normal way to get around this it to place a 0V > voltage source in series with the current path. You can then request > the current from that. In this case you already have that, it is vin, > the vector for current is then vin#branch, so print i(vin) will give > you the current. > > > I don't see this happening in gnucap however (in this case V(0,1) will > not > > work). Am I doing something wrong or is ngspice meant to work this way? I > > went according to the ngspice manual. I'm using Fedora 13 64-bit with > Free > > Electronic Lab groupinstalled. > > gnucap will parse spice for the most part, but it is not the same > especially as it gives more direct access to current power frequency > and other properties of components in the circuit. > > > > > Thanks! :-) > > > > Ashwith J. Rego > > > You might find that this overview of spice will help you better > understand how it works. > http://www.seas.upenn.edu/~jan/spice/spice.overview.html > Especially read the Independent DC sources section for information > about measuring current and voltage. > > I hope this helps. > > --Brennan Ashton > Hi Brennan Thanks. That explained it. Never thought about adding the 0V in series before. Thank you for your help. :) Regards -- Ashwith J. Rego ----------------- My Webpage: http://ashwith.wordpress.com/ Find me on LinkedIn at: http://www.linkedin.com/in/ashwith Follow Me on Twitter at: http://twitter.com/Louisda16th
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