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Free Circuit Simulation Software: What Have You Used?

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Clydes_#1
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What I use
Clydes_#1   8/17/2013 11:01:54 AM
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I use NGSPICE and Kicad for a schematic front end...

 

Yes, as others have said, the simulator is only as good as the models you have.  Google is your friend.

Sheetal.Pandey
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Re: What I use
Sheetal.Pandey   8/17/2013 2:50:45 PM
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Have used pspice simulation. Its good. Its always good to check simulation results before finalizing the gerber for PCB manufacturing.

dick_myers
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Re: Verilog Simulation
dick_myers   8/19/2013 1:24:32 PM
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I use LTSpice for analog simulation and Icarus Verilog coupled with GTKWave for digital simulation.  GTKWave is a top quality waveform viewer, and can compete in useability and features with the best commercial tools. 

Icarus Verilog is a very complete and stable free Verilog simulator.  It's a bit slow for large projects that require long time simulations, but totally adequate for many projects. 

Another free simulator that I've got a lot of mileage with is the Verilator (Perl program), with turns synthesizeable Verilog into C++.  If you have the need for speed, this tool will outperform the even the most expensive commercial simulator.  Using the C++ model of the digital circuit that is output by the Verilator, you can model the external circuitry in C or C++.  You can even make a DLL out of the model + behavior circuitry and call it with a GUI, scripting language, or whatever. 

"Verilator should run any system with GCC and Perl. It is developed on 64-bit SuSE 9.3 and other users report success on Redhat Linux, HPUX, Solaris, and Windows NT under Cygwin (C++ only, no SystemC), and Microsoft Visual C++" And, I believe, OSX.

mike_m
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Re: By far the best
mike_m   8/20/2013 6:40:39 PM
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Without some good test equipment all the modelling software in the world is useless if you can't prove your designs.

For free software: An old copy of ansoft serenade RF designer whichwas bundled with a copy of an antenna text book from the ARRL, LTspice and the excellent free antenna modelling program 4NEC2.

 

Hardware: This along with a Bird RF power meter and slugs, na HP465 precision RF power meter/with head and suitable attenuators, an old analog TEX 465 scope, a HP8558 spectrum analyzer, a HP8640 RF generator with built in freq counter and high power option and an MFJ antenna analyzer along with the solder iron mentioned previously by another individual is all I need for anything from HIGH power RF amplifiers, large multi-element external antennas to small etched internal antenna designs.

Hughston
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Re: By far the best
Hughston   8/22/2013 11:58:21 AM
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When using discrete parts in LTSPICE, look at the models. They are often not the real thing. Add the model card and put the real models in if you want better results. Or make your own model.

Hughston
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Re: By far the best
Hughston   8/22/2013 12:06:12 PM
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You don't always need the model. You might only care about the component tolerance. It depends upon the level of accuracy you are seeking. You can also use a spreadsheet for some calculations. Sometimes that's easier than SPICE.  If you have a lot of unknows in you system, then should you spend a lot of time on the models?

Hughston
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Re: iCircuit
Hughston   8/22/2013 12:23:36 PM
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There is a glaring omission here.  You assume nobody wants to use free software to check their PCB? I check things such as trace impedance, trace differential impedance, trace fusing current, trace dc resistance, resistance increase with temperature, estimate power distribution impedance, via current carrying capacity, via impedance and other things. Analog engineers look at their PCB characteristics too. I use Saturn and Ultracad freeware for this but we have an in house tool for traces impedances.

Is there a freeware equivalent of Hyperlynx, or would that be asking too much?

Sanjib.A
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Re: By far the best
Sanjib.A   8/22/2013 12:28:13 PM
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Thank you for the advice. True...if I have lots of time, usually which is not the case, then a thorough investigation about the models would be possible. In general I tend to simulate to check the concept would or would not work. After ordering the prototype board and before those arrive, the time could be utilized for detailed simulation to be prepared for the mods on prototype...to avoid surprises and frustration :)

jeff99999
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TI's WEBENCH Designer for Circuit Synthesis and Simulation
jeff99999   8/22/2013 1:46:06 PM
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  Have you considered TI's WEBENCH Designer for the analog category?  This is a free on line circuit design tool which includes design synthesis, component selection and Spice simulation.  It also has thermal simulation and the ability to download the design into popular CAD tools.  You can get to it at http://www.ti.com/webench.

Jerome Gouatarbes
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PowerESim
Jerome Gouatarbes   8/23/2013 12:11:02 PM
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PowerESim is a new CAD tool on the Internet for Switching Power Supplies http://www.poweresim.com/ . I heard about it quite recently but it seems to be an interesting tool. Another interesting EE FEA tool is Quickfield from http://www.ocsimize.com/ because it interfaces with LTSpice so it is quite handy.... Best regards, Jgo

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