Hi,
I’m using KiCAD 8, and I’m currently trying to create a plot XY (Vout versus Vin) in simulation but without success for the following circuit.
Any ideas on how can I manage this?
What kind of simulation do you intend to do?
In AC simulation you are plotting Vout/Vin versus frequency. Vin is 1 due to ac=1.
In transient simulation you are plotting Vout and Vin versus time.
Plotting Vout versus Vin in DC simulation does not make sense, as you have blocking capacitors C1 and C2.
Thank you for your response!
I am in the process of transitioning to an open-source simulation software for the electronic courses I teach.
My objective is to conduct a transient analysis and produce a plot of Vin versus Vout.
You can view the example I created using falstad at the following link: https://tinyurl.com/26l4jufd.
I have used Spice in KiCad only few days half year ago, but I suppose that getting something like Lissajous figures is not possible yet. I didn’t noticed any way to change X-axis to something other than default.
I think higher chance for this is in only Spice software like LTspice. I also don’t know the possibilities of Spice used in KiCad. I suppose KiCad uses only a fragment of its possibilities.
I don’t understand your Falstad plot at all, it makes no sense.
What exactly are you trying to show with that plot?
Actually Vin is 1 Vpp due to ampl=500m (assuming the intention is a transient analysis).
This type of plot is useful for assessing the linearity of an amplifier and determining its “valid” signal ranges.
These plots are often used in classes to teach students how to utilize an oscilloscope’s XY mode and to familiarize them with visualizing relationships beyond just “signal vs. time.”
Source: I am also a professor at the same college as @Joao
Just because the plot isn’t clear to you right now doesn’t mean it’s senseless. Let me briefly explain why this plot is interesting. It highlights the region where the amplifier’s output behaves linearly in relation to its input, as well as the boundaries of this linear region, where saturation occurs. This information helps evaluate how close the amplifier operates to its limits.
Yeah 
That makes sense. I did not imply that the plot is useless, but the Falstad thing gives zero information on the plot. It’s just an angled line and anyone’s guess. Add to that that the input as well as the output is labelled “out” doesn’t make things easier.
In this post, line 2, I am talking about small signal AC simulation. In this context your statement is misleading, if not wrong.
When I do an AC simulation, the instance parameter AC=1 may be given to any voltage or current source, thus setting it as the input. All outputs then have to be referenced to this input. So selecting 1 is reasonable, as vout/vin = vout in this case. The refernce phase is assumes to be 0, if not given otherwise. The value 1 does not represent any voltage, just the reference.
Indeed the interface KiCad-ngspice is somewhat limited.
You may use additional ngspice capabilities by scripting, e.g. plotting with gnuplot.
gnuplot.7z (4.5 KB)