Free Spice Simulators

Hello everyone,
I would like to ask if you could recommend a good free spice simulator.
Since I am not into design but more into devices i do not need support of a lot of number of elements but I am more interested in model parameters and post processing of data.
For example gm/gain calculation parameter extraction etc.

Thanks in advance

IMHO,

NGSPICE is the best one out there, in particular for Semiconductor devices.

http://ngspice.sourceforge.net/

LTSpice has the added benefits of integrated schematic
capture and waveform viewing, plus a very active Yahoo!
group with huge archives of circuits and models.

ngspice is one of the better "free" (open) softwares, but
you will need to either get gschem and gwave versions
that play with it, or hand edit your own netlists and figure
out your own plotting.

I have not attempted any sophisticated scripting or post
processing in LTSpice. It does have a language behind it
but I've only ever used the GUI, simply.

Looking at your requirements, Pspice seems to be the better option for following reasons.

-- Firstly Pspice 16.6 version has TCL interface open, where you can play with the database and do lot of post-processing in TCL.
-- Pspice has powerful waveform analysis features. For example cursor lets you know the y values of all traces/plots at particular x value. Moreover you can quickly navigate to local/global maxima/minima of traces. Can quickly create measurements.
-- Pspice supports co-simulation with MATLAB
-- Only Simulator for which most of device manufacturers provide their device models.
-- Provides various advanced analysis. Apart from Monte carlo/Worst case analysis, Stress analysis (called smoke), Optimizer (for design/parameter optimization), Parametric plotter etc.
-- Well integrated with capture schematic entry and Allegro layout.

PSpice, however, is not and has never been "free". Other
than perhaps some crippled student / demo versions.

That's right. It supports upto 75 nodes in free version.
Soathana's requirement was not to use large circuits with high number of nodes, but more on post-porcessing of data for relatively smaller ckts. It might serve the needs better.

LTSpice, TINA-TI, Micro-CAP11,......etc

Thank you all for your suggestions!
I will download and try the software you suggested and provide feedback accordingly...
Cheers

Mouser (electronics supply house) just announced it plans to distribute a free Spice package.

Right now its link can be found in the box at left titled 'EE News, Tips and Resources', 'SPICE simulator free from Mouser August 7, 2014'.