Re: Wanted: LM-709 (Spice model) National Op-Amp


"Paul Rako" <sp_a_mpa_u_l@xxxxxxxxx> wrote in message
news:DzHZe.67$sL3.17@xxxxxxxxxxxxxxxxxxxxxxxxxxxxx
> Well, let me explain why I decide what package to use based on the
> layout package. I spent 25 years as a contractor/consultant. The
> recent rate I charged was 80 to 100 dollars an hour. Believe me,
> a client does not care about SPICE runs. He wants to see hardware,
> little green boards. Only then does his blood-pressure drop. As
> far as they are concerned even drawing a schematic seems silly as
> well as the layout software. Maybe that is why so very many
> companies seem to lose the schematic and layout files and want
> me to improve or fix things with only a Gerber. Then it is off
> to Protel (or some other package I tend not to enjoy) because it
> can import a Gerber to the layout package and at least lets you
> wing things from there.
>
> Now in my mind the most important principle about ECAD is connectivity.
> That what you draw on the schematic will show up as a flight line
> in the rats nest and that any gate swaps or re-annotation done
> in layout can be back-annotated. Having a separate SPICE schematic
> violates this principle. Now you have something whose coherence is only
> assured by human inspection.
>
> Now I sure do appreciate the difficulty in making SPICE sources in a
> schematic for layout or alternatively, connector parts for something
> that will be SPICEed. And Jim, I think when people talk about the
> the misery of using SPICE Orcad Capture it is the "occurances" vs
> "instances" issues I mentioned. You are one of several hard-core
> designers I have met that prefers PSPICE schematics to capture. There
> are enough of you that Cadence still lets you download the PSPICE
> capture program even for 10.5 release.
>
> As to getting the board parasitics back, then you have to leave the
> lumped element SPICE world and go to 2 or 3-D field solvers like
> hyperlynx. This is generally referred to as signal integrity.
> High-zoot hyperlynx that can handle lossy transmission lines is
> 48 grand or so. And good old Orcad has a hyperlynx output export,
> even though Hyperlynx is now a Mentor tool.
>
> Judging our test is just observing the schematic and what one has to
> do to get good results. Pretty much just read the thread when
> you get around to it and comment on the methodology and results.
> We want to enter a schematic Jim Williams built many years go and
> see how various SPICE packages do. I also have some PSPICE stuff that
> did not converge and will post that and bear the withering criticism
> that I did something stupid or had a bad model. But the group has
> to understand it is not just about convergence-- it is about
> having the real board agree with the SPICE results.
>
> Paul
>

<Since material top posted am cutting out previous>

"Having a separate SPICE schematic
> violates this principle. Now you have something whose coherence is only
> assured by human inspection."

Why do you assume this?

Aren't LVS or "Layout versus Schematics" tools known in your work?

Robert


.