Author Topic: Simulation Only Software  (Read 858 times)

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Offline merelyuseful

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Simulation Only Software
« on: June 28, 2020, 02:45:53 pm »

Before we start I'll explain myself a little.  I am relatively inexperienced at electronics but I am a software developer with many years learning new programming languages behind me.  I'm not afraid to learn new packages and I have bashed away at some of the worst software in the world when I had to if it got the job done. 

Anyway.  I am working on a design for an audio amp for and I was using NI's MiltiSym on line to set things up.  The GUI does exactly what you expect it to and everything makes sense.   This was perfect, I could amend their op amp model to use the parameters off the datasheet I was using,  set up my circuit and simulate quickly.  The platform has a learning curve that can be overcome in minutes.  Unfortunately they have a 25 component limit on the trial version and the commercial version costs thousands of pounds which I can't justify. 

Now here's my question:  Is there anything else out there that doesn't carry the same price tag as a Rolex watch that is as easy to learn?   I have incredibly small amounts of time to do this.  I have a very demanding job and a very demanding family so I get to spend a maximum of 25 minutes on something before I get interrupted.  Once I hit the limit on Multisym, I started looking for different online tools and tried a few but none were as easy to learn as (sorry  - I've just been interrupted twice while writing this) Multisym.  I have tried a few but they either wouldn't let me change the op-amp parameters or when I tried loading in the TI spice model,  the simuiation died (I think due ti NGSpice / PSpice incompatibilities).  I've learned enough Eagle to hate it thoroughly but it's looking like the only alternative at the moment.

Am I just going to have to accept that I will need to learn Spice in fifteen minute chunks for the next five years and delve further into the horrible Eagle than is good for any sane person or is there anything out there that is actually intuitive?



Online Ian.M

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Re: Simulation Only Software
« Reply #1 on: June 28, 2020, 04:32:22 pm »
Why not see how you get on with LTspice?   Its certainly not intuitive, but it wont cost you anything* except the time it takes to learn it, and is a full  SPICE program with no arbitrary node or model limits, with a *LOT* of third party resources available including comprehensive user contributed model libraries.

Its got a fairly comprehensive universal OPAMP model- just plug in the parameters and level of modelling required.  After installation, from your LTspice working folder, navigate to examples\Educational\UniversalOpamp2.asc to find out how to configure your OPAMP.   

Many third party un-encrypted PSpice models are LTspice compatible, and many others only fail due to minor syntax differences that can easily be overcome by hand-editing the model's netlist.   

* its zero cost, including professional use, unless you are in the semiconductor manufacturing business.

Offline tggzzz

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Re: Simulation Only Software
« Reply #2 on: June 28, 2020, 06:00:27 pm »
The two "heavyweight" analogue simulation packages worth looking at are LTSpice and MicroCap. Both will have a learning curve, since they are complex subtle tools for a complex subtle task.

You need to determine what you want to get from a simulation package.
  • If you are interested in understanding the general operation of a type of circuit, and understanding which components/parameters are/aren't important, then you can use fairly generic component models available in plain-vanilla spice.
  • If you are interested in determining the error bounds for your specific circuit with your specific components will work before you build it, then you will need to be very careful about the models you choose.

In any case, you will need to understand the limits of what is and isn't being modelled. For example
  • many opamp "macromodels" will model the basic parameters, but not all of the subtle parameters, e.g. noise as a function of frequency, or overload recovery.
  • a spice resistor is just that and no more, but a real resistor will have parasitic capacitance and inductance, and those are critical at RF. But then at RF the track geometry is vital, e.g. see microwave distributed element filters where spice is the wrong tool to use.
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Offline ebclr

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Re: Simulation Only Software
« Reply #3 on: June 29, 2020, 01:12:53 pm »

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