These are the models that I am calling.

@Stefan Schippers Trying to plot Id-Vd curve for NMOS with sweeping Vgs. But not able to plot waveform inside xschem window. Please see attached gif file and suggest what might be wrong here.

Hello everyone, I have a question regarding mixed signal (MS) simulations. I was part of a webinar a few months ago where the organizers worked with the tool eSim to run mixed signal simulations. I would like to know if it is possible to run MS simulation for schematic circuits only with Xschem and ngspice? Do you have material about it? Kind regards,

Hello everyone, I was trying to analyze the corner impact on the circuit and I need to plot transient waveforms in different corners. I would appreciate it if anyone let me know how should I do that in xschem. Also, where can I find the script for plotting ngspice signals in matlab? Thanks @Tim Edwards

Hello, is there an easy way to disable the code blocks? for example if I have a block of spice code to run a parameterised sweep but want to disable it while I use a different analysis? I don't want to delete it or go through and comment out all the lines if I can help it

Hi, I am trying to simulate a basic nfet circuit however, I am not sure why nothing happens when I click the Simulate button. I am trying to do transient analysis however nothing happens. I have also attached the spice file. I think it should be importing the .lib file for sky130 transistor models but it is not doing so. I have to do that manually and run ngspice manually from the terminal to make it work.

Is there a way to add current/voltage source with Sine wave or pulse transient specifications? I just saw arithmetic and pwl. I believe arithmetic might do it but I am not sure how I would specify the amplitude and frequency

Hello, I am trying to plot the transconductance of an OTA versus the DC differential voltage, varying from -0.9 to 0.9 Volts. In LTSpice, it is quite easy, due to the .step directive. I'm performing the AC simulation for each DC voltage appliet at the input of the differential pair, as it can be seen in the attached figures. However, in XSCHEM/NGSpice I did not get success. I think I need to construct two vectors, one for the voltages and other for the AC magnitude (phase is irrelevant for my study). And thereafter plot magnitude versus voltage. Can anyone show me how to deal with the vectors in order to make this plot? PS: in the plot, the current is shown, but since the AC differential voltage is 1.0 V, the numerical value is equal to the transconductance.

Just for adding some information, the simulation in LTSpice was usinng another 180nm model.

This is the code that is not working

Does the solid curve above show AC magnitude vs common mode voltage ? What frequency do you want the AC magnitude to refer to? AC analysis calculates circuit parameters vs frequency. If you want to plot vs common mode voltage you need to choose a frequency point... Not sure what you want to do...

May be LTspice has a .ac syntax to calculate only a single frequency point, and may be you can do this with ngspic by specifying start, stop and number of divisions such that only one frequency is calculated. At least this is my understanding

I want to plot the AC magntude just for 1 kHz. The .AC simualtion is just an artifact to plot the transconductance. This work well in LTSpice

I think if I find the correct sintax for fill the 'magnitudes' vector just with the magnitude of the AC current, I will get success.

I have also problems to force ngspice to calculate only one frequency point. the syntax

.ac dec 1 1k 1k

will calculate 0 frequency points and no data is generated...

I did it, by changing the code to this:

Is there a maximum lenght for a vector? Because if I change the step to 0.01 and the vector lenght to 181 (181 points), the result is erroneous.

I have a working example here: schematic also attached. It plots the ac gain of a differential amplifier at 1kHz vs common mode (VCM) voltage. May be you can adapt to your test bench.

If I want to generate a lookup table for an nfet then I would need to perform nested dc simulations of all the transistor ports along with parametric sweeps of 'W' and 'L', is there an simple way to do it in ngspice.

Where can I get information about the minimum and maximum widths and lengths and area about the transistors.

@Stefan Schippers, I am trying to annotate the current , other parameters in schematic using back annotation command : xschem annoate op but annotation is not happening? is this issue with xschem version? Can you tell which version of xschem i need to update. I am using xschem version: XSCHEM V3.1.0

I am looking for some transistor operating point parameters, just wanted to confirm that whether they are represented by these variables in the spice model: Transconductance(gm), Output resistance(ro),Overdrive voltage(vdsat). Please correct me if I am wrong.

Hello all, I'm trying to plot a vector of voltage versus voltage (using the 'plot' command), but I'm still using just 19 points. The plotting is correct, but when I try to use more points in order to get a more refined graphics, the NGspice is plotting the points of one vector versus the points of the other, which means a straight line (wrong result). Does NGSpice have a maximum number of points allowed for a vector? Is there any way to plot vectors with more points? Thank you in advance.

How to avoid resetting the temperature value when using 'alterparam' and then subsequently using 'reset' .

What can I do if I want to make a simulation with jfet p-channel? I don't find that component in the devices list. Thanks

Hi @Stefan Schippers, my xschem which I always built from source from the latest GitHub seems to be missing all the picture icon buttons underneath the menu bar at the top of the window which I've seen in various videos/screenshots. Why is that?

Is it possible to array instances and connections in xschem? And if so, how do you connect all VSS instances to a common net for example?

Hi @Stefan Schippers, we are looking for the following xschem netlisting feature, not sure, if this is already existing. We would like to be able to netlist for LVS with certain elements removed (leaving the connecting wires open or short-circuit). Means, we need • a cmdline switch to indicate netlisting for LVS • an lvs_ignore property on symbols, which can be set to none/short/open (none doing nothing, short = remove element, short nodes, open = remove element, keep wires floating) Is this someting you could implement? That would be very helpful!

Did you know? You can visually display differences between schematics, in particular current schematic with it's saved version:

hello does anyone know how I can do a mixed signal simulation in xschem?