Simulator surround circuit (Qucs) is a software simulator, electronic circuits, and is open source under the authorization of the GNU General Public published. This application will give you this will allow the circuitry of Your by a graphical user interface, draw and behavior signal. signal and perturbation, it's simulation. Simulations also digital by Verilog or VHDL is supported.

Qucs from an ever-growing collection of analog components, and digital, including sub-circuits SPICE support.