Based on three open source software packages; Spice3f5 the most famous and used electronic circuit simulator, Cider a mixed-level simulator that already includes Spice3f5 and adds a device simulator to it and Xspice, an extension to Spice3 that provides code modeling support and simulation of digital components through an embedded event driven algorithm. Ngspice is a part of gEDA project but it is distributed separately from mainstream gEDA applications. Ngspice is now one of most versatile spice implementation as it can deal with a very large set of netlists functionalities. It implements various classes of analysis:

Ngspice implements the usual circuits elements, like resistors, capacitors, inductors (single or mutual), transmission lines and a growing number of semiconductor devices like diodes, bipolar transistors, mosfets (both bulk and SOI), mesfets, jfet and HFET and EKV model but, this model, cannot be distributed with the package since its license does not allow to redistribute EKV source code. The NgSpice license is the BSD license.

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. So far we were working on the GUI and on some basic simulation features. In fact there is now a kind of useful user interface for 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 are available. Anyway, a lot of work has to be done and thus we are looking for people who want to support the project. For more informations about Qucs click here.
 

           

Spice OPUS is a free analog circuit simulator engine specially suited for optimization tools. It is based on UC Berkeley's SPICE 3f4 and is a recompilation of the original Berkeley source code. Later Georgia Tech Research Institute's XSpice mixed-mode simulator was added to the Berkeley code (like NGSpice). The simulator includes an interpreted programming language called Nutmeg, which allows interactive Spice sessions. The graphical part of the program was rewritten but the original syntax commands was preserved, enabling any script compatibility with other Spice compilations. Spice OPUS is developed and maintained by the Faculty of Electrical Engineering at the University of Ljubljana, Slovenia. For more information about Spice OPUS click here. Note: There is the first complete guide (a book!) to analog circuit design using the circuit simulator software package Spice OPUS "Circuit Simulation with Spice OPUS".

             

TkGate is a graphical editor and event-driven simulator for digital circuits with a tcl/tk-based interface. Supported circuit elements include basic gates (AND, OR, etc.), tri-state gates, adders, multipliers, registers, memories and mos transistors, also includes ttys and modules for hierarchical design. The TkGate simulator, called VERGA (VERilog simulator for GAte), is a discrete time simulator with time advancing in discrete units called "epochs". All delay must be an integer number of epochs. The simulator supports continuous simulation, single step simulation (by clock or epoch) and breakpoints. The Verga simulator is normally used through the TkGate interface, but it can also be run by itself directly on text Verilog files. The simulator can be controlled either interactively or through a simulation script. Memory contents can be loaded from files, and a microcode/macrocode compiler (gmac) is included to create TkGate memory files from a high-level description. Gmac is a simple microcode and macrocode compiler which can be used to create memory files for TkGate. You can write declarations to define your own microcode and macrocode. The current version of Gmac is fairly simple; no attempt is made to handle arbitrary instruction sets with complex addressing modes, but it should be sufficient to create simple micro and macro programs. TkGate saves files in a Verilog-like format. TkGate supports a subset of the complete Verilog specification. For more information click here