Qucs-S: Qucs with SPICE

Download links

The latest stable release is Qucs-0.0.20. It is based on stable Qucs-0.0.19: (Installation instructions...)

Contibuition guide

Qucs-S is open for everyone's contribution. See here for contribution guide.


Simulation example with Qucs-S and Ngspice

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Qucs-S is also a research software. Check our publication list.

What is Qucs-S?

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. It has advanced RF and AC domain simulation features, but most of the existing industrial SPICE models are incompatible with it. Qucs-S is not a simulator by itself, but it requires to use a simulation backend with it. The schematic document format of Qucs and Qucs-S are fully compatible. Qucs-S allows to use the following simulation kernels with it:


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Main features



Debian repository

Debian(7,8, and 9) and Ubuntu(14.04 and 16.04) repositories are available for Qucs-S. Packages are built with automatic Open Build Service (OBS) tool from OpenSUSE team. Go to download repository You need to perform the following steps to add this repository in system (for Debian 9). For othe distributions simple replace the URLs. If you have problems with adding repository in your system you can download and install the *.deb package manually with dpkg:

dpkg -i qucs-s-0.0.19S_amd64.deb
You may need to install the following dependencies: lib4qt4-qt3support, ibqt4-svg, ngspice

RPM packages for CentOS and Fedora

You need to simple add reposotries using the yum package manager. Let's consider example for CentOS:

Building from source

If binary packages are not available for your distrubution, then you will need to build Qucs-S from source: The complete command sequence to build Qucs-S is following:

tar xvfz qucs-s-0.0.20.tar.gz
cd qucs-s-0.0.20
mkdir builddir
cd builddir
cmake ..
make install

The last command make install should be executed from root user. It will install Qucs-S into default prefix /usr/local/. Use -DCMAKE_INSTALL_PREFIX=... to override the default locationNo additional configure options are needed now.

Slackware SlackBuild

Slack Build script is available for Slackware distribution. It will download and compile Qucs-S automatically. You will obtain the binary Qucs-S package. Perform the following steps to install Qucs-S:
  1. Clone this repository:
    git clone https://github.com/ra3xdh/QucsS.SlackBuild
  2. Run SlackBuild as root:
    cd QucsS.S.SlackBuild
  3. Install txz package with installpkg command


You need to use binary installer for Windows. You need to download and install Ngspice and/or XYCE manually from official websites: http://ngspice.org/ https://xyce.sandia.gov respectively.

Important note for Ngspice on Windows: Unpack Ngspice ZIP package strictly to the C:\SPICE location. Otherwise XSPICE model will not work! If you are getting strange errors with Ngspice on Windows and cannot ot simulate even simple circuit, please check that Ngspice is installed strictly in C:\SPICE . All Ngspice packages including offcial should be installed in a such way.

It's recommended special build of Ngspice-26 for Windows Ngspice26_QucsS.zip . Default Ngspice package also will work but it may have some limitation. Custom Ngspice build solves the following issues:



Run qucs-s from the the command line or launch Qucs-S icon in your desktop environment menu after the installation. You will need to select default simulation backend at the first run. You can change it later in the application settings.


Launch Qucs-S in the system Start menu. You will also need to select default simulator on the first application start. You will need to set default simulator at the first run. Correct simulator paths setting is necessary for Windows.

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Contribution guide

Steps to contribute

Source code of the Qucs-S is hosted at the Github in the following repository: https://github.com/ra3xdh/qucs_s. You need to clone this repository if you wish to contribute.

git clone -b current https://github.com/ra3xdh/qucs_s
cd qucs_s
git checkout -b your_feature
Use CMake to compile Qucs-S. After you make changes, prepare a pull request to Qucs-S repository.

Branching model

Currently there are two main branches in my home Qucs repository:

Release tarball is obtained from master with some Bash script. I distribute only Qucs-GUI and some utilities with Qucs-S package.

My changes only concentrated on GUI side, and you need to rebuild GUI only to test Qucs-S. You may take Qucsator from usual Qucs installation.

Build instruction (development branches)

For qucs-s-stable you need to set WITH_SPICE cmake key. Autotools will not work. Perform the following commnads to build all: git clone https://github.com/ra3xdh/qucs_s/
cd qucs_s
mkdir build
cd build
cmake .. -DCMAKE_INSTALL_PREFIX=/some_path

Then install and launch qucs-s executable. (to top...)



Qucs-S is not a simple circuit simulator, but also a research software. Please cite our articles, if you are using Qucs-S in your research.
  1. Brinson, M. E., and Kuznetsov, V. (2016) A new approach to compact semiconductor device modelling with Qucs Verilog-A analogue module synthesis. Int. J. Numer. Model., 29: 1070-1088. (BibTeX)
  2. D. Tomaszewski, G. Głuszko, M. Brinson, V. Kuznetsov and W. Grabinski, "FOSS as an efficient tool for extraction of MOSFET compact model parameters," 2016 MIXDES - 23rd International Conference Mixed Design of Integrated Circuits and Systems, Lodz, 2016, pp. 68-73. (BibTeX)
  3. M. Brinson and V. Kuznetsov, "Qucs-0.0.19S: A new open-source circuit simulator and its application for hardware design," 2016 International Siberian Conference on Control and Communications (SIBCON), Moscow, 2016, pp. 1-5. (BibTeX)
  4. M. Brinson and V. Kuznetsov, "Improvements in Qucs-S equation-defined modelling of semiconductor devices and IC's," 2017 MIXDES - 24th International Conference "Mixed Design of Integrated Circuits and Systems, Bydgoszcz, 2017, pp. 137-142. (BibTeX)
  5. M. Brinson and V. Kuznetsov, "Extended behavioural device modelling and circuit simulation with Qucs-S" International Journal of Electronics, 2017, pp.1 - 14 (BibTeX)