Quite Universal Circuit Simulator

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Quite Universal Circuit Simulator
Logo QUCS.png
QUCS screen shot.png
Screenshot of QUCS
Original author(s) Michael Margraf, Stefan Jahn et al.
Initial release December 8, 2003 (2003-12-08)
Stable release 0.0.18 / 31 August 2014; 8 months ago (2014-08-31)
Written in C++
Operating system Mac OS, Windows, GNU/Linux, Solaris, FreeBSD
Type EDA
License GNU General Public License v2+
Website qucs.sourceforge.net

Quite Universal Circuit Simulator (Qucs) is an open-source 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.

Qucs supports a growing list of analog and digital components as well as SPICE sub-circuits. It is intended to be much simpler to use and handle than other circuit simulators like gEDA or PSPICE.

Analysis types[edit]

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.

Features at a glance[edit]

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.

Tool suite[edit]

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 [1] is used. For circuit optimization (minimization of a cost function), ASCO [2] is configured and run.


The following categories of components are provided:

  • Lumped components (R, L, C, amplifier, phase shifter, etc.)
  • Sources
  • Probes
  • Transmission lines
  • Nonlinear components (diodes, transistors, etc.)
  • Digital components
  • File containers (S-parameter datasets, SPICE netlists)
  • Paintings

There is also a Component library that includes various standard components available in the market (bridges, diodes, varistors, LEDs, JFETs, MOSFETS, and so on).

Transistor models[edit]

QUCS provides many transistor models. These include:

  • 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)
  • JFET

Short Description of mathematical Functions[edit]

The following operations and functions can be applied in QUCS equations:[3]

  • max(x,y) returns the greater of the values x and y
  • min(x,y) returns the lesser of the values x and y
  • rms(x) root mean square of a vector
  • sum(x) sum of values in vector
  • prod(x) product of values in vector
  • diff(y,x) differentiates vector y with respect to x
  • diff(y,x,n) differentiates vector y with respect to x n-times
  • integrate(x,h) integrates vector x numerically assuming a constant step-size h
  • real(x) real part of complex number
  • imag(x) imaginary part of complex number
  • abs(x) absolute value, magnitude of complex number
  • mag(x) same as abs(x)
  • norm(x) square of mag(x)
  • conj(x) conjugate complex
  • phase(x) phase in degree
  • angle(x) phase in radians
  • arg(x) same as angle(x)
  • deg2rad(x) converts degrees to radians
  • rad2deg(x) converts radians to degrees
  • dB(x) voltage decibel
  • dbm(x) convert voltage to power in dB
  • dbm2w(x) convert power in dBm to power in Watts
  • w2dbm(x) convert power in Watts to power in dBm
  • sqr(x) square (x to the power of two)
  • sqrt(x) square root
  • exp(x) exponential function to basis e
  • ln(x) natural logarithm
  • log10(x) decimal logarithm
  • log2(x) binary logarithm
  • sin(x) sine
  • cos(x) cosine
  • tan(x) tangent
  • sinh(x) sine hyperbolicus
  • cosh(x) cosine hyperbolicus
  • tanh(x) tangent hyperbolicus
  • arcsin(x) arcus sine
  • arccos(x) arcus cosine
  • arctan(x[,y]) arcus tangent
  • arccot(x) arcus cotangent
  • coth(x) cotangent hyperbolicus
  • ceil(x) rounds to the next higher integer
  • fix(x) truncates decimal places from real number
  • floor(x) rounds to the next lower integer
  • round(x) rounds to nearest integer
  • sign(x) computes the signum function
  • sinc(x) returns sin(x)/x and one at x=0
  • fft(x) computes the fast fourier transformation (FFT) of the vector x
  • ifft(x) computes the inverse fast fourier transformation (IFFT) of the vector x

See also[edit]


  1. ^ "FreeHDL index Page". Freehdl.seul.org. Retrieved 2012-03-01. 
  2. ^ "ASCO project :: homepage". Asco.sourceforge.net. Retrieved 2012-03-01. 
  3. ^ "Mathematical functions for QUCS index Page". gnu-darwin.org. Retrieved 2014-04-15. 

External links[edit]