LTSpice: Slow on noise sims with foreign opamps

Joerg, The .asc file you sent privately... the .asc (symbol) shows only three connections to the OpAmp... five are required. Do you have latest version of LTspice? I vaguely recall a discussion of problems with OpAmp2.

Looking at the netlist, the LTspice-proper pin order is...

IN+ IN- V+ V- Vout

Your library has...

-IN +IN V- V+ Vout

So you have it bass-ackwards >:-} ...Jim Thompson

Opamp2 is the one that has five pins and that works with all the opamps I had tried, except for the Burr-Brown/TI parts. So I copied Opamp2.asy and made another Opamp2TI.asy out of that, now it all works fine. That way I don't have to muck with the model files because that's always a dicey proposition.

Yup, I figured it out yesterdas, see my other reply in the thread. But by then the barbie was ready and that's when the end of the workday is not negotiable with my better half.

To avoid a proliferation of symbols (*) I always adjust the pin order in the subcircuit declaration... but keep the original order following the ';' (comment) character in case I need to go back... or share with someone else.

My standard OpAmp (or comparative) symbol pin order is...

IN+ IN- Vout V+ V-

Also gates, as in...

A B ... Q V+ V-

(*) I already have 804 custom symbols >:-}

I've got to break my better half of piling things on high shelves. Yesterday, during a "get this down for me honey" request, a dish drainer try came loose from her pile, hit me in the head, then spun around and cut the back of my hand open :-(

She's just exactly 5' tall, but won't listen when I tell her... just come and get me and _I'll_ put it away for you. She just stands "on-tippy-toe" and shoves stuff on top of the stack. The cookie sheet pile can be hazardous to one's health :-) ...Jim Thompson

anymore)

opamp in

stepping

ballpark

constellations, input

what gives

take a

of a

before. No

hands-on guys.

one degree

as

ID#

with

included

because

not

the 4140

case,

on

fit LTSpice.

(Rearranged

rearrangement

by V1.

by V2.

not?

ain't

It's easier to tweak the model. That way it's right the next time.

Cheers

Phil Hobbs

in anymore)

opamp in

stepping

ballpark

constellations, input

what gives

take a

front of a

before. No

hands-on guys.

one degree

fast as

ID#

with

included

because

did not

tonight.

the 4140

case,

run on

fit LTSpice.

(Rearranged

rearrangement

by V1.

by V2.

not?

ain't

Yup. Self-standardization keeps the mind from twisting >:-} ...Jim Thompson

I'd rather not touch those if possible. It feels like messing with a datasheet. After all, a SPICE model is usually something released by a manufacturer unless you build your own from component data.

That's a good method, although it does add to the clutter of SPICE directives on the sheet.

That's a lot. But as an IC guy you live SPICE, us circuit guys live CAD. I have a ton of custom symbols for the schematic editor.

Oh yeah! The situation is quite similar here. She it petite and I am the tall guy. But my wife keeps things lean, if it hasn't been used in x years it has to go. At least it's not going to the trash, if in good condition then it'll become a thrift store donation. Our kitchen doesn't have shelves, it's all humongous cabinets but the top sections don't carry much. Mostly things like Christmas decorations that only have to come out once a year.

Pin ORDER doesn't change the model... it just matches up the symbol's pin order to the subcircuit declaration.

If you were a regular Spice user you'd know all about the importance of pin order and subcircuit declarations.

As far as "messing", you "messed" with the symbol pin order didn't you ?:-)

I'd rather have symbol consistency. In your world some days the base of a tranny would be a collector ?? ...Jim Thompson

How is that? On MY schematics will you see any "directives" other than .LIB ??

My symbols are _schematic_ symbols just like yours. Many of mine are "test instruments" ;-)

...Jim Thompson

I wish I had your faith...

Sno-o-o-ort! ...Jim Thompson

-- | James E.Thompson, CTO | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona 85048 Skype: Contacts Only | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at

In my world a new package and CAD symbol gets created if even one lone pin is different from customary. But never in the datasheet, and I usually never veer from the outline in that datasheet for pin descriptors and such.

If you meant "changed in the .lib file" then no, that's not what I want to do.

Fraidy cat ?:-}

I have over 90 different process vendors to contend with. Thus I don't generically call all those libraries when I load PSpice. The schematic lists ("directive" in LTspice speak) only those I need.

And over 5000 "corners" >:-} ...Jim Thompson

You just made my point... Why should I have more than one symbol for all the thousands of 5-pin OpAmps?

Now, admittedly, in your PCB world there may be many different PACKAGE outlines, thus different symbols on the schematic.

I don't have that problem, everything I do is at device-level >:-} ...Jim Thompson

Because else one has to muck with the text in the lib file. That's a no-no in a controlled design environment. Just imagine I had a file called ThompsonAmp.lib and the pin order in there is not right for my simulator. Suppose I'd change that in the ThompsonAmp.lib file and now it works. How should I store that file? If it's then stored as ThompsonAmp.lib and an auditor from the FDA or another agency finds out, oh boy. Even if I store it under another name the action of changing something in there must be justified in writing and documented if working on a sensitive project.

You still be an amateur when it comes to understanding simulators :-( ...Jim Thompson

Like I said yesterday. Something isn't hooked up right in the model.;-)

If anyone feels the need to be told how stupid they are, Thompson is always eager to assist.