1. Qucs Vs Ltspice
  2. Qucs Download
  3. Qucs Tutorial

Happy Easter to everybody!

Quite Universal Circuit Simulator (Qucs) is a free-source electronics circuit simulator software. It is used to create a circuit with a graphical user interface. It replicates the large-signal, small-signal and noise behavior of the circuits. Installation of Qucs is explained in this manual. Qucs repository to publish documentation generated with Doxygen 0 0 0 0 Updated Jan 23, 2016. Top languages C Python Shell Perl OpenEdge ABL. Most used topics.

  • If you have old schematic didn't display correctly and/or crash when you add a simple resistor/component. TL;DR (quick hack) o remove extra/qt4 (uninstall qt4) o rebuild aur/qt4 (make it compile: comment patches (2 in total) that can't be applied, the 1st one and the kubuntu 14.) / install qt4 o rebuild qucs / install / enjoy.
  • Qucs-S is a spin-off of the Qucs cross-platform circuit simulator. 'S' letter indicates SPICE. The purpose of the Qucs-S subproject is to use free SPICE circuit simulation kernels with the Qucs GUI. It merges the power of SPICE and the simplicity of the Qucs GUI. Qucs intentionally uses its own SPICE incompatible simulation kernel Qucsator.

Latest News

New Forum


11th August 2020

QucsaiA new forum as well asa new homepage with own domainis now available. Thanks a lot for this to Daniel Dieterle!
Please register and publish all new posts there.The old forum will stillbe reachable for some time.

Version 3.3.2 released

15th July 2020

QucsStudio version 3.3.2 is now available.Besides many new features (e.g. electromagnetic field simulator),many historical flaws were fixed. For example a single m as unithas not the meaning of milli anymore, i.e. now 3m = 3 and 3mm = 3e-3.Future versions will not be able to load old schematic files.Therefore, it's recommended to open all existing schematic and data display fileswith version 3.3.2 and save them afterwards.So within a project, select the files with mouse button and shift key,drag'n'drop them into the editor und press the Save all button.
The biggest thanks go to all who donate to this project, as you are the onesthat made this version happen!

Forum online

5th September 2019

A forum for discussingQucsStudio topics is now available on the internet. Users can nowregister and talk about their problems, experiences and wishes.

New optimization examples uploaded

13th April 2019

The optimization package now contains many new example, available in the sectionexamples.

New tutorials available

6th October 2018

Two new tutorials by Jose Manuel Campelo available in the sectionpublications.

Version 2.5.7 released

14th July 2018

In order to celebrate the anniversary, QucsStudio version 2.5.7is now available. Users can look forward to many new features.Furthermore, the examples were updated and new video links arelocated in the section screenshots

Qucs Vs Ltspice


15th anniversary

May 2018

15 years ago the Qucs project started. Congratulations on the birthday!

Support section added

1st August 2016

This homepage now contains a list with tasks that are needed for thedevelopment of this project. Everybody who wants to help is called tohave a look into the support section.

Result of feature survey published

1st March 2016

The feature survey has just been closed.The result can be seen here.

New tutorials available

16th February 2016

A tutorialby Jose Manuel Campelo is now ready to download.Gunthard Kraus also upgraded histutorialon his homepage.

Tutorial V1.6 available

14th December 2015

version 1.6 of the german tutorial by Gunthard Kraus available.It now contains a chapter about Harmonic Balance simulations.Qucs

Feature survey started

7th December 2015

A survey has just started to find new features for the future development of QucsStudio.Please click here and take part!

New homepage

30th November 2015

A completely new design for this homepage has been released. Hopefully you like it.

Tutorial V1.5 available

6th November 2015

version 1.5 of the tutorial by Gunthard Kraus available

Qucs Download

Russian tutorial available

2nd November 2015

Russian version of Gunthard Kraus tutorial available. Many thanks to Vladimir Gololobov.


Tutorial available

Qucs Tutorial

25th February 2015

first version of the german tutorial by Gunthard Kraus available

Wavepad for mac. .

10th anniversary

May 2013

10 years of Qucs development. Happy birthday!


First QucsStudio version released


1st February 2011

QucsStudio version 1.0.0 released

First Qucs version released

8th December 2003

Qucs version 0.0.1 released

Qucs development started

May 2003

The original Qucs project was born.
Basic electronic:‎ > ‎

Quite universal circuit simulator Qucs

posted Aug 11, 2016, 7:35 PM by Marc Aubry [ updated Aug 27, 2016, 5:56 PM]
Because my university period is now fare away behind me, my maths and electronic theory are very very rusty and U=R*I and P=U*I .are the only calculation i'm able to do without having to remember my maths :)
Of course browsing on the net give you access to an unlimited already calculated and working schematics but they can be very frustrating because you don't have the proper capacitor or resistor value to breadboard it. You can always tweak some value on your breadboard prototype but it can be very tedious and frustrating.
So why not simulating the circuit before breadboarding it?
Browsing on the net i found quite a lot of online circuit simulator like partsim, Circuit lab, falstad and plenty more.
Most of them look very similar and are based on spice model but they are all Online simulator cloud based with account creation and all the circus. which is not practical in my remote working environment where internet is everything but reliable.
This is a pretty cute java applet that give you a quick visual look on tons of electronic circuit.Very easy to use and no need of registration or what so ever. no add a well:)
Looking for stand alone circuit simulator i found out QUCS Quite univeral simulator
What's Qucs?
'Qucs stands for Quite Universal Circuit Simulator. So far Qucs is not yet finished, but it is already packed with features. Take a look at the screenshots to get a feel for what it can do.
Qucs is an integrated circuit simulator which means you are able to setup a circuit with a graphical user interface (GUI) and simulate the large-signal, small-signal and noise behaviour of the circuit. After that simulation has finished you can view the simulation results on a presentation page or window.
  • Qucs, briefly for Quite Universal Circuit Simulator, is a circuit simulator with graphical user interface (GUI). The GUI is based on Qt® by Digia®. The software aims to support all kinds of circuit simulation types, e.g. DC, AC, S-parameter, Harmonic Balance analysis, noise analysis, etc.
  • Qucsator, the simulation backend, is a command line circuit simulator. It takes a network list in a certain format as input and outputs a Qucs dataset. It has been programmed for usage in the Qucs project but may also be used by other applications.
The Qucs GUI is well advanced and allows setting up schematics and presenting simulation results in various types of diagrams. DC, AC, S-parameter, noise and transient analysis is possible, mathematical equations and use of a subcircuit hierarchy (with parameterised subcircuits) are available. Qucs can also import existing SPICE models for use in your simulations'..

..'While Qucs is well developed, we still strive to improve the project, and will always welcome offers of help. Qucs doesn't just need help with programming, it also needs graphics, high quality example schematics, tutorials for the website and lots more.
Qucs comes with a huge array of components and models including HICUM, BSIM2, BSIM3, and soon BSIM6. It also provides many semiconductor based components and models such as OpAmps, Diodes, MOSFETs, PMOSFETs and many more. Some example schematics can be found here which demonstrate some of the abilities of Qucs, and many more examples are provided with the program.'

My practical application of QUCS:

My bedside lamp just die. It was a thyristor like 40w dimmer lamp.
I would love to replace the 220vac thyristor dimmer by a 12Vdc led dimmed by a simple potentiometer.
Using the same principle as my previous project Transformerless Day/Night Controlled Led step light, I can power 8 led from my led strip roll via a transistor and dimmed it via a potentiometer.
What do i have in stock:
  • 250k Ohm potentiometer scraped from my dead lamp
  • 8 led from my led strip roll
  • 1 transistor BC547b
  • 1 NA02-T2S12 12VDC 2W power supply

My led strip sub circuit:

There is no components for my 8 strip led in the Qucs component library.
I have to make a sub circuit with qucs library component who behave as close as possible like my led load.
each led work in 12 v and use 18 ma and have an internal resistor. I assume that this kind of led is 3.6 V.
Looking in the Qucs component library i select the blue Led with 3.3V and 20ma.
each led in the sub circuit will be driven by a resistor of the following value: R=(12v-3.3V)/0.018A=483 Ohm
I now able to make a DC simulation using my sub circuit to validate my high led circuit.
I1 is a current probe to measure the current flowing in the circuit and the Parameter sweep is going to change the value of the DC power V1 from 1v to 12v in 1 v increment.
The sub component High led is pointing to the Qucs file of the led circuit already defined above HighLedSub.sch.
I can now run the DC simulation and draw the following diagram.

I can now draw my final circuit diagram including my BC 547 b transitor and my 250k potentiometer and run a DC simulation with a Parameter sweep changing the resistance of the potentiometer.
The parameter sweep is going tochange the rotation in degre of the pot in between 0 deg to max 240 deg ( as define in the pot component library wit a maximum resistance of 250k ohm of the pot.
I1 is going to measure the total current draw by the circuit.
I2 the current drawn by the pot and I3 the current drawn by the led sub circuit.
i had some Label Vpot to measure the voltage at the potentiometer output, Vbase to measure the base voltage of the transistor andVcol to measure the colector voltage of thetransistor.
Running the simulation in Qucs i can now draw the following diagrams:

Hurrah Hurrah !!!! It's seem to work.
The first diagram on the top left show me in blue the Vcol / Pot value.
At 0Ohm no current pass between collector and emitter. and 250 Ohm the transistor is saturated and 124ma flow in between collector and emitter and we have a nice curve in between 50 ohm and 200 ohm.

After bread boarding the circuit i measure the current with my tester between the led and the collector and obtain almost the same result
I1 =0.140ma vs 0.135ma from Qucs
and the lamp dim exactly as expected with a nice curve.


The Bread board prototype work exactly like the Qucs simulation.
I can tweak any value from the simulation to emulate any behavior of the circuit without to have to burn down any components.
There is as well a good library of schematics located in the Qucssharedocqucs folder.
I assembled this circuit in my original bed lamp stand and i have now a dimmed led bed lamp of of 1.7W instead of the original 40W.