As you may know, I’m a big fan of simulation software including some online freebies and Linear’s LTCSpice which I’ve blogged about before. However, the Qucs project (http://qucs.sourceforge.net) has improved to the point that it is quite usable and really very slick. The program is made to run under Qt on Linux, but it will also run with Cygwin quite nicely.

Features include:

• Simulation not done by Spice (but support for Spice net lists)
• Analog and Digital simulation (with support for VHDL and with some wrangling, Verilog)
• Command line simulator back end for use with other programs (Qucs uses a GUI)
• S-Parameter, AC, DC, Transient, and noise analysis
• Very powerful way to create graphs and charts
• Filter and attenuator synthesis
• Smith charts

The program is actively developed and more features are planned.

If you want a good idea of what it can do, look at this tutorial.