> Qucs is a GPL circuit simulator. And if you want the GUI option, you might want to try out QucsStudio, which uses Qucs under the hood, and is free to use, but binary-only.<p>Huh? I used Qucs many moons ago and it definitely was complete with GUI.<p><a href="https://qucs.sourceforge.net/screenshots.html" rel="nofollow noreferrer">https://qucs.sourceforge.net/screenshots.html</a><p>Unfortunately Qucs is unmaintained, probably doesn't compile anymore on newer distributions and its binaries were therefore removed from many repositories. Another problem: Qucs was released as GPL while QucsStudio, which uses its sources, has been kept closed by the authors; I smell a GPL violation here.
It's a shame that circuit simulators, especially those derived from SPICE, have tended toward closed-source. It's nice that there are several free-as-in-beer options available, but a good lesson in the consequences of permissive open-source licenses. SPICE predates copyleft licensing, so software that was once open has disappeared into proprietary versions.<p>LTspice (sponsored by Analog Devices) is closed-source.
The recently-released QSpice (sponsored by Qorvo) also closed-source.
QucsStudio was taken closed-source by Qucs' original author, and he's not commented on his intentions in this decision.<p>Big companies typically open-source software when it's not part of their strategic business value, and offers community engagement benefits and good press. LTspice is kind of an advertisement for AD's chips. AD and Qorvo aren't remotely in the software and EDA business, so their decision to keep them closed is even more puzzling, but I guess the instinct of hardware companies is guard everything.
On windows there is LTSpice which is free, has a lot of models, but not open source and ngspice which is open source but it does not have a GUI (although i heard that it can be used with KiCAD).<p>So i really don't underestand, what would be the advantage of using Qucs ?
As an amateur I always default to CircuitJS, it's a great learning resource<p><a href="https://www.falstad.com/circuit/circuitjs.html" rel="nofollow noreferrer">https://www.falstad.com/circuit/circuitjs.html</a>
You should consider using qucs-s <a href="https://ra3xdh.github.io/" rel="nofollow noreferrer">https://ra3xdh.github.io/</a> a fully open-source fork of qucs still currently maintained and improved.
When talking about open source tools, here are some:<p>KiCad may be used as a schematic entry tool for ngspice, especially for discrete or PCB-based electronics. You may watch several simulation examples (including oscillators) here: <a href="https://forum.kicad.info/t/simulation-examples-for-kicad-eeschema-ngspice/34443" rel="nofollow noreferrer">https://forum.kicad.info/t/simulation-examples-for-kicad-ees...</a>. KiCad integrates ngspice internally, but may also provide external ngspice with netlists for simulation.<p>Another GUI to ngspice is XSCHEM, especially useful for IC design work (see <a href="https://xschem.sourceforge.io/stefan/index.html" rel="nofollow noreferrer">https://xschem.sourceforge.io/stefan/index.html</a>). Device models are available by the Open Source PDKs from Google/Skywater, Google/GF, or IHP. A growing community is supporting digital, analog or mixed-signal design flows.<p>QUCS-S (<a href="https://ra3xdh.github.io/" rel="nofollow noreferrer">https://ra3xdh.github.io/</a>) is a GUI for ngspice or XyCE.<p>Indeed device models have to be added manually to the devices in the circuit schematic, when invoking ngspice via KiCad or QUCS-S, except for some basic devices with integrated models. Models are provided by device makers, distributors or web sites like this one: <a href="https://ngspice.sourceforge.io/modelparams.html" rel="nofollow noreferrer">https://ngspice.sourceforge.io/modelparams.html</a> .
Can it simulate oscillators? Many of the lower end or cheaper systems fall apart when it comes to modelling real world radios. Probably because in reality everything is a bit capacitive/inductive and there is a noise floor at any given frequency.
Wokwi is free open source and neat with an MIT license <a href="https://github.com/wokwi/avr8js">https://github.com/wokwi/avr8js</a> <a href="https://wokwi.com" rel="nofollow noreferrer">https://wokwi.com</a>
surprising to see nobody's mentioned ngspice, wr-spice, or omedit (the openmodelica editor), all of which are open-source free software capable of simulating circuits<p>(though ngspice has had some licensing issues in the past i think those are fixed now)<p>you can get spice models for just about any part on the market and use them in ngspice, wr-spice, or the original berkeley spice, though not falstad's circuit.js or omedit<p>relevant to this week's tantalizing superconductor news, wr-spice is the only one with a decent josephson junction model
Not open source but Free:
Micro-Cap 12
<a href="https://web.archive.org/web/20230219052113/http://www.spectrum-soft.com/index.shtm" rel="nofollow noreferrer">https://web.archive.org/web/20230219052113/http://www.spectr...</a>