Quite Universal Circuit Simulator (Qucs) is a

free-software Free software, libre software, libreware sometimes known as freedom-respecting software is computer software distributed under terms that allow users to run the software for any purpose as well as to study, change, distribute it and any adapted ...

electronics circuit simulator software application released under

GPL The GNU General Public Licenses (GNU GPL or simply GPL) are a series of widely used free software licenses, or ''copyleft'' licenses, that guarantee end users the freedom to run, study, share, or modify the software. The GPL was the first c ...

. It offers 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. Originally, Qucs was composed of a circuit simulator "qucs-core", now ''Qucsator'', and a GUI for schematic entry and plotting. The usage patterns, as well as the emphasis on RF design, were inspired by some commercial tools of the time. Later, support for other simulators has been added to cover

VHDL VHDL (Very High Speed Integrated Circuit Program, VHSIC Hardware Description Language) is a hardware description language that can model the behavior and structure of Digital electronics, digital systems at multiple levels of abstraction, ran ...

Verilog Verilog, standardized as IEEE 1364, is a hardware description language (HDL) used to model electronic systems. It is most commonly used in the design and verification of digital circuits, with the highest level of abstraction being at the re ...

and

SPICE In the culinary arts, a spice is any seed, fruit, root, Bark (botany), bark, or other plant substance in a form primarily used for flavoring or coloring food. Spices are distinguished from herbs, which are the leaves, flowers, or stems of pl ...

engines to some extent. At this stage both devices and circuits were specific to the targeted simulator or specific versions thereof. In particular, neither was Qucsator based on SPICE, nor did a SPICE based simulator replace Qucsator at any given time. In the meantime, Qucs has been forked to accommodate specific needs, most notably Caneda and Qucs-S. Today, Qucs ships a list of analog and digital components including sub-circuits for use with a variety of simulators. It is intended to be much simpler to use and handle than other circuit simulators like

gEDA The term gEDA refers to two things: # A set of software applications ( CAD tools) used for electronic design released under the GPL. As such, gEDA is an ECAD (electronic CAD) or EDA (electronic design automation) application suite. gEDA ...

PSPICE OrCAD Systems Corporation was a software company that made OrCAD, a proprietary software tool suite used primarily for electronic design automation (EDA). The software is used mainly by electronic design engineers and electronic technicians to ...

. The current roadmap aims to decouple schematic representation, device modelling and preferred simulator choices by means of adopting concepts from the IEEE1364 industry standard.

Analysis types

Analysis types include

S-parameter Scattering parameters or S-parameters (the elements of a scattering matrix or S-matrix) describe the electrical behavior of linear electrical networks when undergoing various steady state stimuli by electrical signals. The parameters are useful ...

(including

noise Noise is sound, chiefly unwanted, unintentional, or harmful sound considered unpleasant, loud, or disruptive to mental or hearing faculties. From a physics standpoint, there is no distinction between noise and desired sound, as both are vibrat ...

), AC (including noise), DC, transient analysis,

harmonic balance Harmonic balance is a method used to calculate the steady-state response of nonlinear differential equations, and is mostly applied to nonlinear electrical circuits. It is a ''frequency domain'' method for calculating the steady state, as opposed ...

(not yet finished), digital simulation (

and Verilog-HDL) and parameter sweeps.

Features

Qucs has a graphical interface for schematic capture. Simulation data can be represented in various types of diagrams, including Smith chart, cartesian, tabular,

polar Polar may refer to: Geography * Geographical pole, either of the two points on Earth where its axis of rotation intersects its surface ** Polar climate, the climate common in polar regions ** Polar regions of Earth, locations within the polar circ ...

, Smith-polar combination, 3D cartesian, locus curve,

timing diagram Timing diagram may refer to: * Digital timing diagram A digital timing diagram represents a set of signals in the time domain. A timing diagram can contain many rows, usually one of them being the clock. It is a tool commonly used in digital el ...

and truth table. The documentation offers many tutorials, reports 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 Verilog-A is an industry standard modeling language for analog circuits. It is the continuous-time subset of Verilog-AMS. A few commercial applications may export MEMS designs in Verilog-A format. History Verilog-A was created to standardize the ...

interface, support for multiple languages (

GUI Gui or GUI may refer to: People Surname * Gui (surname), an ancient Chinese surname, ''xing'' * Bernard Gui (1261 or 1262–1331), inquisitor of the Dominican Order * Luigi Gui (1914–2010), Italian politician * Gui Minhai (born 1964), Ch ...

and internal help system), subcircuit (including parameters) hierarchy, data post-processing using equations and symbolically-defined nonlinear and linear devices.

Tool suite

Qucs consists of several standalone programs interacting with each other through a GUI. The GUI is used to create schematics, setup simulations, display simulation results, writing VHDL code, etc. The analog simulator, gnucsator, is a command line program which is run by the GUI in order to simulate the schematic which you previously setup. It reads a netlist file augmented with commands, performs simulations, and finally produces a dataset file. It can also report errors. The GUI includes a text editor which can display netlists and simulation logging information. It is handy to edit files related to certain components (e.g. SPICE netlists, or Touchstone files). A filter synthesis application can help 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). A component library manager gives access to models for real life devices (e.g. transistors, diodes, bridges, opamps). These are usually implemented as macros. The library 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 can steer other EDA tools. Analog and mixed simulations can be performed by simulators that read the Qucsator netlist format. For purely digital simulations (via VHDL) the program FreeHDL or Icarus-Verilog can be used. For circuit optimization (minimization of a cost function), ASCO may be invoked.

Components

The following categories of components are provided: * Lumped components (

resistors A resistor is a passive two-terminal electronic component that implements electrical resistance as a circuit element. In electronic circuits, resistors are used to reduce current flow, adjust signal levels, to divide voltages, bias active e ...

inductors An inductor, also called a coil, choke, or reactor, is a passive two-terminal electrical component that stores energy in a magnetic field when an electric current flows through it. An inductor typically consists of an insulated wire wound into a ...

capacitors In electrical engineering, a capacitor is a device that stores electrical energy by accumulating electric charges on two closely spaced surfaces that are insulated from each other. The capacitor was originally known as the condenser, a term st ...

amplifier An amplifier, electronic amplifier or (informally) amp is an electronic device that can increase the magnitude of a signal (a time-varying voltage or current). It is a two-port electronic circuit that uses electric power from a power su ...

, phase shifters, etc.) * Sources * Probes * Transmission lines * Nonlinear components (

diodes A diode is a two- terminal electronic component that conducts electric current primarily in one direction (asymmetric conductance). It has low (ideally zero) resistance in one direction and high (ideally infinite) resistance in the other. ...

transistors A transistor is a semiconductor device used to Electronic amplifier, amplify or electronic switch, switch electrical signals and electric power, power. It is one of the basic building blocks of modern electronics. It is composed of semicondu ...

, etc.) * Digital components * File containers (S-parameter datasets,

netlists) * Paintings There is also a component library that includes various standard components available in the market (bridges, diodes,

varistors A varistor (a.k.a. voltage-dependent resistor (VDR)) is a surge protecting electronic component with an electrical resistance that varies with the applied voltage. It has a nonlinear, non- ohmic current–voltage characteristic that is similar ...

LEDs A light-emitting diode (LED) is a semiconductor device that emits light when current flows through it. Electrons in the semiconductor recombine with electron holes, releasing energy in the form of photons. The color of the light (correspo ...

, JFETs,

MOSFETs upright=1.3, Two power MOSFETs in amperes">A in the ''on'' state, dissipating up to about 100 watt">W and controlling a load of over 2000 W. A matchstick is pictured for scale. In electronics, the metal–oxide–semiconductor field- ...

and so on).

Transistor models

Qucs supports transistor models, some need to be added by hand. Some have been tested, these include * FBH-HBT * HICUM L0 v1.12 * HICUM L0 v1.2 * HICUM L2 v2.1 * HICUM L2 v2.22 * HICUM L2 v2.23 * MESFET (Curtice, Statz, TOM-1 and TOM-2) * SGP (SPICE Gummel-Poon) * MOSFET * JFET * EPFL-EKV MOSFET v2.6.

Qucs-S

Qucs-S is a fork of Qucs that supports the SPICE-compatible simulator backends of

Ngspice ''Ngspice'' is an open-source mixed-level/ mixed-signal electronic circuit simulator. It is a successor of the latest stable release of Berkeley SPICE, version 3f.5, which was released in 1993. A small group of maintainers and the user community ...

, Xyce, SpiceOpus, in addition to Qucsator. Version 2 was released in August 19, 2023.

References

External links

*
FreeHDL home page

Icarus Verilog home page

Win32 Binaries for Qucs and freehdl

QucsStudio
{{CAD software Free electronic design automation software Free software programmed in C++ Electronic design automation software for Linux Electronic circuit simulators Engineering software that uses Qt