Good open source circuit simulation software?

[alxptt]

For those of us who prefer to use open source, what's the best simulators I can expect to find? And also, what feature sets should I expect them to be missing compared to the 'standard' simulators?

On a side note, I am also wondering if there are many other simulators that actually show charges flowing in the circuit. The simulator at falstad.com/circuit is a great example of this. You can see everything happening in real time. Although it's not a requirement for me, this sort of feature is really helpful for wrapping my head around a new design principle!

[tggzzz]

What do you need to simulate? Analogue? Digital? RF? Thermal? Multiphysics? ...

[alxptt]

What do you need to simulate? Analogue? Digital? RF? Thermal? Multiphysics? ...

Just analogue circuits! No need for any of that other stuff -- although RF may come in handy later on. It's not a requirement, though.

[hagster]

I like QUCS, but I haven't really done anything too challenging with it.

http://qucs.sourceforge.net

[RoGeorge]

https://en.wikipedia.org/wiki/SPICE

[T3sl4co1l]

SPICE itself is open, the most popular historically being Berkeley 3f5 (the basic models and analyses) and Georgia Tech XSPICE (mixed mode simulation).  These are command line and text oriented: you input a plaintext netlist, let the analysis chug away, and out spews piles and piles of data, or some crude text graphs.  Ideal for an add-on interface and postprocessor...

Ngspice is a current development based on SPICE, incorporating new features, and optimized for current technology.

QUCS is a different thing, so beware of compatibility.  It's unclear to me if you can drop in off-the-shelf models.  If you have to test parts and write your own models, that raises the bar several orders of magnitude, as far as required knowledge and effort.  So it really pays to have consistency here (and why it's so offensive that many companies provide models only in proprietary e.g. PSPICE, HSPICE, LTspice, encrypted, etc. forms).

Tim

[janoc]

QUCS is a different thing, so beware of compatibility.  It's unclear to me if you can drop in off-the-shelf models.  If you have to test parts and write your own models, that raises the bar several orders of magnitude, as far as required knowledge and effort.  So it really pays to have consistency here (and why it's so offensive that many companies provide models only in proprietary e.g. PSPICE, HSPICE, LTspice, encrypted, etc. forms).

Tim

I have tried to use QUCS but never managed to get anything meaningful out of it - crashes, random hangs, the solver gets stuck/hangs/whatever ... Oh and that assumes you actually manage to start the simulation in the first place - the "helpful" messages from the checker that it has failed (and no more detailed information why did it actually fail) are infuriating.

I am a Linux and open source guy myself but in this regard I am staying with LTSpice. That one at least works.

[bson]

LTspice is probably the best free UI based option right now, but it's not open source.  But do keep an eye on the ngspice integration being added to KiCAD.  I gave it a spin the other day and while the simulator UI is very basic and is missing a whole bunch of stuff (tabs in the UI are still blank and unimplemented for example), what was there did seem to work and it has a couple of nice features not in LTspice.  One among them is a simulator UI control for component values, making it easy to say adjust a resistor by dragging a slider.  But it has a ways to go before it's an alternative to LTspice.  ngspice however is a very capable simulator (it puts LTspice to shame), so wrapped in a good UI (and the KiCAD schematic capture is miles ahead of LTspice) I see no reason why it wouldn't be quite usable and a good alternative to LTspice.

[janoc]

Yeah, I am planning to have a look at this once the new Kicad release is out.

On the other hand, the advantage of LTSpice is that there are models for it. You can have the best simulator UI in the world and the best solver behind it but it will be useless unless you can find models for the semiconductors you use. Can you use LTSpice models in ngspice?

[Yansi]

I like QUCS, but I haven't really done anything too challenging with it.

http://qucs.sourceforge.net

I would recommend QUCS STUDIO instead. As compared to the "plain QUCS" it happens to work, more acceptably.

[janoc]

I like QUCS, but I haven't really done anything too challenging with it.

http://qucs.sourceforge.net

I would recommend QUCS STUDIO instead. As compared to the "plain QUCS" it happens to work, more acceptably.

Well, given that I am a Linux user and Qucs Studio has this on the webpage:
"Currently QucsStudio supports Windows® only.", it is not likely I am going to be able to use it.

Moreover, that seems to be a one man incompatible fork of Qucs, so support for models and such is likely going to suck even more.

[exe]

None that I'm aware of. I tried all of them a few years ago, found nothing useful. Qucs, for example, had problems simulating step response (there was a fork to fix that).

[Bassman59]

Can you use LTSpice models in ngspice?

The models of the Linear Tech switch-mode power supply devices and such work only in LTSpice. (They are in a custom binary format.)

[Canis Dirus Leidy]

ngspice however is a very capable simulator (it puts LTspice to shame), so wrapped in a good UI (and the KiCAD schematic capture is miles ahead of LTspice) I see no reason why it wouldn't be quite usable and a good alternative to LTspice.

Alternatively you can use gschem with spice backend for netlist generation, but this is Linux-only solution.

[newbrain]

ngspice however is a very capable simulator (it puts LTspice to shame), so wrapped in a good UI (and the KiCAD schematic capture is miles ahead of LTspice) I see no reason why it wouldn't be quite usable and a good alternative to LTspice.

Alternatively you can use gschem with spice backend for netlist generation, but this is Linux-only solution.

Just for kicks, I tried gschem on the WSL (Windows Subsystem for Linux) in Windows 10. Using Xming as X11 server, it seems to work.
In general I had very few problems with normal userspace programs (mostly compilers/make and the like, though).

[Yansi]

I like QUCS, but I haven't really done anything too challenging with it.

http://qucs.sourceforge.net

I would recommend QUCS STUDIO instead. As compared to the "plain QUCS" it happens to work, more acceptably.

Well, given that I am a Linux user and Qucs Studio has this on the webpage:
"Currently QucsStudio supports Windows® only.", it is not likely I am going to be able to use it.

Moreover, that seems to be a one man incompatible fork of Qucs, so support for models and such is likely going to suck even more.

After spending quite a few afternoons trying to do a non-linear simulations in QUCS, I would like to make a point, that no matter what, QUCS jsut sucks beyond usability. QUCS Studio sucks too, but is notably better.

Run it in Wine.   

[alxptt]

I'll use VirtualBox to keep the gross proprietary stench away from my pristine FOSS-only Arch Linux system, thanks. xD

[Yansi]

Use whatever you want, just don't curse on "proprietary" software that works way better than most of the opensource garabage.

In case of the QUCS, the "proprietary" one man show "QUCS Studio" is so much better in terms of performance, functions and usability, compared to the "crowdsourced" QUCS,  it just blows ones mind.

I needed it for non-linear (harmonic-balance) simulations, and the QUCS was beyond unusable junk. QUCS Studio at least fixed a lot of issues and the user interface is muuuuch better, however still didn't work as expected.

[alxptt]

Uh, I don't think the FOSS crowd is for you -- sure, there's a difference between quality and license goodness-of-a-product, but the license thing is a matter of principle (and pragmatism) for me. If you don't care about software licensing, that's fine with me tho.

[CustomEngineerer]

I'll use VirtualBox to keep the gross proprietary stench away from my pristine FOSS-only Arch Linux system, thanks. xD

 

[tacpilot]

tinkered with LTspice on wine - clunky GUI and issue with saving files - fixed save issue with wine from ppa. looks nice but using it still left me feeling deprived..

tinkered with Qucs 0.0.19 - native Linux compat. and nice GUI but had issues with some models like zeners not working and limited doc's. Is not spice compatible but its qucsator engine is nicely geared for RF and hi freq's.

looked at Qucstudio - uses only the Qucs GUI with its own custom engine, and another win only -- kept looking elsewhere

finally found Qucs-S - looks to be the best of many worlds - is a spin off from Qucs by some of the Qucs dev team - GUI improvement and supports multiple backends making it spice compatible while maintaining back compat with qucsator.

tinkered with Qucs-S-0.0.21 - so far so good .. smooth .. all the models I have tried work. Their website is polished and doc's appear to be robust - looks to be the direction the Qucs project is heading. Will be the simulator I have settled on.

removed statement about 0.0.20 -- it looks to be the first incarnation of Qucs-S

both can be found here - https://ra3xdh.github.io/

online docs - https://qucs-s-help.readthedocs.io/en/latest/Intro.html#

Hope this helps .. Cheers