SPICE Models

[T3sl4co1l]

Seeing as there's very little discussion here specifically about simulation, I'll just start a general thread, and put things here as they come up.

Here's a CD4001B model -- the real deal!  The transistors look to be accurately modeled and scaled, and the ESD protection quirks are even included.  You can't get a better model of the chip using nitric acid and a microscope!
https://www.seventransistorlabs.com/Images/CD4001_TR.ckt

Tim

[tautech]

I started a topic on simulation last year Tim and we got enough in it to point users in the right direction and then it fizzled out. Do we attempt to keep it all together or just drop a link in each so users can hunt out what they need.
https://www.eevblog.com/forum/beginners/circuit-simulation-(sticky)/

[T3sl4co1l]

Sure, link in whatever you think is useful.

Tim

[chris_leyson]

Hi guys, I would definitely be up for some spice discussion. Only last week I was looking for spice models for some obsolete RF transistors, BFRQ22, BFR91, BFR96, BFT95 and BFT96 it's difficult enough finding data sheets let alone spice models. It turns out that Cadence have these parts in their Pspice library, a total of 33,000 parts in all ! Had a look on their Pspice site www.pspice.com but you can't download individual models and it seems that you have to install Pspice or Pspice Lite. Also, you don't get all of the models with Pspice Lite. Updates for Orcad 16.6 stopped over a year ago so users are now forced to upgrade to Orcad 17.2 if they want Pspice updates, just seemed like an odd way of doing things.

[Cerebus]

On a related topic, does anybody have any experience of software that spits out a SPICE model when handed a set of measurements from a curve tracer or similar characterisation instrument? I've heard of "modsim" but it appears to be abandonware nowadays. Are there others? Any open source efforts?

[T3sl4co1l]

That sounds like an ill-posed problem.  There are definitely tools for specific cases, like diodes and transistors.  The enterprise ones, typically seen in mfg models, include MODPEX (mid 90s, IR used 'em).  Think I've seen some others, can't remember offhand.

If you can find 'em, they aren't going to be cheap, or have permissive licensing.

There are general curve-fitting tools, for vectorizing graphs, but the result might not be analytically sound.

Tim

[rfbroadband]

such a tool does not exist! You can find tools that can help you do curve fitting and automatic measurements...but you need lots of experience, time and money (equipment) to create accurate models that you can trust.

[Cerebus]

That sounds like an ill-posed problem.  There are definitely tools for specific cases, like diodes and transistors.  The enterprise ones, typically seen in mfg models, include MODPEX (mid 90s, IR used 'em).  Think I've seen some others, can't remember offhand.

Yeah, "Modpex" - I mis-remembered the name. Now I have the right name I re-found the page I found previously that says "The Modpex program is no longer commercially available".

I did say "curve tracer" which kind of implies diodes and transistors (I suppose you might stretch it to include NPNP type devices but I wasn't thinking of those).

Altium Designer has a 'wizard' that seems to do some SPICE parameter extraction for BJTs, but I've never been anywhere near it as I've never used AD for simulation. Truthfully, I'd never even considered using the built-in simulator as by the time I get anywhere near Altium the design, simulation and breadboarding/prototyping stage is over.

such a tool does not exist!

Well clearly I and Tim just imagined Modpex and the others then.

You can find tools that can help you do curve fitting and automatic measurements...but you need lots of experience, time and money (equipment) to create accurate models that you can trust.

Gosh darn it, and I thought you'd be able to do it with an AA battery and a DT830!

[Jay_Diddy_B]

Hi,

I have used a tool for modelling power MOSFETs from the datasheets. I found it on the Yahoo Groups LTspice  group.

Here is a screenshot of the About dialogue box:



It might help you find it.

Jay_Diddy_B

[Cerebus]

It might help you find it.

At the moment I'm more interested in people's experiences using this kind of thing than in trying to find one to use, but by the lack of any apposite replies it doesn't look like there is any experience of them out there. With people asking for models of older parts I thought that a parameter extraction tool might be an interesting option but obviously they are going to be of little use if they don't produce at least passable models without extensive manual fettling. That is, if one has the skills to build a SPICE transistor model from just the datasheet* then you don't need such a tool and you don't need to ask for models (except on days you're feeling lazy). Ergo, the people asking for models of older parts probably don't have the skills to do it themselves and could do with a software 'leg up'.

As at least one tool (Modpex) was good enough for one or more of the manufacturers then I would have though that these tools ought to be up to scratch, but in the absence of any experience it's really difficult to judge. i.e. It's more speculation than judgement at this stage.

*Assuming the datasheet is extensive enough to form the basis of a model, many aren't.