[sdiy] Becoming better at understanding difficult analog schematics

[Jay Schwichtenberg]

It really depends on what you want. A lot of time I do what you do and 
that is just through a circuit into LTSpice and see what it does verses 
sit down and figure out the math. Also you understand the fact that this 
is a simulation and might or might not give accurate results. Lots of 
noobs go 'I simulated something and the circuit worked but the 
implementation doesn't' and wonder why.

I did contract HW/SW and one of the places I worked there were senior 
EEs doing Spice simulations of circuits going from 5 to 30 GHz. These 
were real simulations actually writing Spice code to get things close to 
being functional before prototyping.  That was beyond rocket science for me.

Jay S.

On 5/16/2024 1:29 PM, Tom Wiltshire wrote:
> Maybe I'm a newb, but I don't agree about "more than likely add your 
> own models". There's a lot of useful stuff you can do in LTspice 
> without going near making your own models.
>
> Perhaps we're just working towards different objectives? Mostly I use 
> it for testing ideas instead of breadboarding, generating frequency 
> responses for networks that would be a pain to work out manually, 
> checking filter responses, that sort of stuff.
>
> I definitely don't think it's going to give me a perfect answer - the 
> first time I got the ideal op-amp model to spin out to a 15KV output 
> voltage firmly dissuaded me of that, and that's surprisingly easy to 
> do. The concept of "op-amps with no supply rails" is pretty weird, if 
> you're coming from a more practical background - and since it clearly 
> leads to behaviour which is far from realistic, I did wonder a bit why 
> they included them at all. Now I'm better at it, I know when I can use 
> the basic models because it doesn't matter and when I need something 
> that actually has a rail limit. So yes, I totally agree that you need 
> some understanding of what the thing is doing and what you're looking 
> at - but 15KV output is a give-away to *anyone*, right, newb or not?!?
>
>
>> On 16 May 2024, at 19:58, Jay Schwichtenberg via Synth-diy 
>> <synth-diy at synth-diy.org> wrote:
>>
>> I wouldn't recommend noobs using simulation without them having some 
>> understanding of it. Main reason without knowing how it works they 
>> assume that a simulation is going to give you the perfect answer or 
>> close to it.
>>
>> To get good simulations you really need to know what you are doing 
>> and more than likely make your own models. A lot of the models for 
>> components are simple and don't go into the details of the 
>> components. So that can make a big difference in the simulation.
>>
>> There are things like noise, power supply ripple, transmission lines, 
>> PCB layout ... that you have to manually add to get really good 
>> simulations that they have no idea how to do.
>>
>> Jay S.
>>
>>
>> On 5/16/2024 11:21 AM, Paulo Constantino via Synth-diy wrote:
>>> What about the Falstad simulator? It's the best for quick and dirty 
>>> sims!!!!!!!
>>>
>>> On Thu, May 16, 2024 at 7:11 PM Chris McDowell via Synth-diy 
>>> <synth-diy at synth-diy.org> wrote:
>>>
>>>     Simulation, yeah! I learn a ton from popping stuff into LTSpice
>>>     and try out anything new or novel there first.
>>>     Cheers,
>>>     Chris
>>>
>>>>     On May 16, 2024, at 8:21 AM, ben gebhardt via Synth-diy
>>>>     <synth-diy at synth-diy.org> wrote:
>>>>
>>>>     
>>>>     Not sure if mentioned already, but I learn alot by simulating
>>>>     circuits and then doing time and frequency domain analysis.
>>>
>>
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