Screenshot of QUCS
|Original author(s)||Michael Margraf, Stefan Jahn et al.|
|Initial release||8 December 2003|
0.0.19 / 22 January 2017
|Operating system||macOS, Windows, Linux, Solaris, FreeBSD|
|License||GNU General Public License v2+|
Quite Universal Circuit Simulator (Qucs) is a free-software electronics circuit simulator software released under GPL. It gives you the ability to set up a circuit with a graphical user interface and simulate the large-signal, small-signal and noise behaviour of the circuit. Pure digital simulations are also supported using VHDL and/or Verilog.
Analysis types include S-parameter (including noise), AC (including noise), DC, Transient Analysis, Harmonic Balance (not yet finished), Digital simulation (VHDL and Verilog-HDL) and Parameter sweeps.
QUCS has a graphical interface for schematic capture. Simulation data can be represented in various types of diagrams, including Smith-Chart, Cartesian, Tabular, Polar, Smith-Polar combination, 3D-Cartesian, Locus Curve, Timing Diagram and Truth Table.
The documentation offers many useful tutorials (WorkBook), reports (ReportBook) and a technical description of the simulator.
Other features include the transmission line calculator, Filter synthesis, Smith-Chart tool for power and noise matching, Attenuator design synthesis, Device model and subcircuit library manager, Optimizer for analog designs, the Verilog-A interface, Support for multiple languages (GUI and internal help system), Subcircuit (including parameters) hierarchy, Powerful data post-processing possible using equations and symbolically defined nonlinear and linear devices.
Qucs consists of several standalone programs interacting with each other through the GUI.
The GUI is used to create schematics, setup simulations, display simulation results, writing VHDL code, etc.
The analog simulator is a command line program which is run by the GUI in order to simulate the schematic which you previously setup. It takes a netlist, checks it for errors, performs the required simulation actions, and finally produces a dataset.
The text editor is used to display netlists and simulation logging information, and to edit files included by certain components (e.g. SPICE netlists, or Touchstone files).
The filter synthesis application can be used to design various types of filters.
The transmission line calculator can be used to design and analyze different types of transmission lines (e.g. microstrips, coaxial cables).
The component library manager holds models for real life devices (e.g. transistors, diodes, bridges, opamps). It can be extended by the user.
The attenuator synthesis application can be used to design various types of passive attenuators.
The command line conversion program tool is used by the GUI to import and export datasets, netlists and schematics from and to other CAD/EDA software. The supported file formats as well as usage information can be found on the manpage of qucsconv.
Additionally, the GUI steers other EDA tools. For digital simulations (via VHDL) the program FreeHDL  is used. For circuit optimization (minimization of a cost function), ASCO  is configured and run.
The following categories of components are provided:
There is also a Component library that includes various standard components available in the market (bridges, diodes, varistors, LEDs, JFETs, MOSFETS, and so on).
QUCS provides many transistor models. These include: