Pspice Master Class

[analag]

How about it guys...training the newbies how to use simulators in a realistic way. Especially when using it to look deeply into tube circuits.

 

[12afael]

ltspice rulez!!!, I hate pspice.

 

[clintrubber]

[quote author="analag"]How about it guys...training the newbies how to use simulators in a realistic way. Especially when using it to look deeply into tube circuits.[/quote]
We could argue about whether newbies should be using simulators in the first place, but that's not what you meant, right ? I recall the PPR-remark that people should have filled at least quite a few back-of-envelopes before starting a circuit-simulator.

In case the idea is aimed at 'people-new-at-circuit-simulators': good idea !

 

[Kamel]

good idea, i will maybe understand how this monster goes, does it run on Mac OSX machine?

 

[analag]

[quote author="12afael"]ltspice rulez!!!, I hate pspice.[/quote]

I agree....
http://www.linear.com/designtools/software/index.jsp
those interested should download and install
http://www.duncanamps.com/technical/ltspice.html
follow these instructions if you want play with tube models.

It's very easy to use and adding models is effortless.

 

[12afael]

It's very easy to use and adding models is effortless.

that´s the great part and the fact that you can pass audio through the circuit!

here you can find pots, opamps, opto couplers and others models.
http://tech.dir.groups.yahoo.com/group/LTspice/


it would be good idea to make a folder with all the useful libraries for audio, I have added several trancistors to my library, I could share it.

 

[analag]

I made a pretty good library of tubes too. These I have used to build a number of microphones, mic pre, compressors and so on.

 

[12afael]

here is the bjt and jft libraries

http://www.twin-x.com/groupdiy/albums/userpics/cmp.zip
just unzip it on the cmp folder and restart ltspice.

some of the models were taken from this page
https://obvody.feld.cvut.cz/katalog/index.php?idTyp=2&idPodtyp=13
and from others softwares.

 

[Ian MacGregor]

I have been using quite a bit of LTSpice for transistor stuff. I would love to learn more about the software. For instance, if I have a discrete opamp, is there a way to represent it as a single symbol in a overall system schematic?

When designing a feedback system (inverting, non-inverting, DC servo, etc) how do you guys find open loop gain, loop gain etc? I have seen and tried different methods (such as using a very large inductor and large cap in the feedback path to allow for DC feedback, but blocking AC feedback). Any better ways?


Ian

 

[12afael]

here are a couple of winks tutorials.

http://www.soldersmoke.com/kl7r/
http://www.freewebs.com/ocarnal/demos/wave.htm
http://www.freewebs.com/ocarnal/demos/diviseur.htm
http://www.freewebs.com/ocarnal/demos/passehaut.htm
http://www.freewebs.com/ocarnal/demos/fet.htm

I have been using quite a bit of LTSpice for transistor stuff. I would love to learn more about the software. For instance, if I have a discrete opamp, is there a way to represent it as a single symbol in a overall system schematic?

it is posible with a sub circuit, but I don´t know how :sad: . on the yahoo group is a model of the JE990 DOA.

 

[Dan Kennedy]

JE990 DOA?

As in Dead on Arrival?

Probably a pretty simple model...

 

[SSLtech]

DOA as in Discrete Op-Amp...

DOn't worry, I always read it as dead-on-arrival, and have to re-think it every time someone uses that term... -I wish they wouldn't, because DOA already has such a well-established meaning, but then I have to remind myself that not everyone is a native English speaker...

Keith

 

[PRR]

> if I have a discrete opamp, is there a way to represent it as a single symbol in a overall system schematic?

For simple sanity-checks: any recent sim will have a '741 or LF411 model you can drop-in.

If you peek inside, you will see that most op-amp sim blocks are NOT the complete amp. Typically a diff-pair input and then some ideal Gm and VCVS blocks plus a cap and some diodes. The story is that simulating a complete op-amp, especially with several on the plan, is far too CPU-intensive to be practical.

That's obviously changed, since modern CPUs are 10X-100X faster than when PC-based sim with opamps started. And a few vendors have improved models.

An awful lot of opamp models will NOT model power pin currents. They have a phantom ground reference which the actual chip lacks. Useless for several important chores.

Even with improved models, be real dubious about distortion.

There IS a way to compile a schematic to a block. I never figured it out.

 

[Dan Kennedy]

Don't you just love geek humor, it's so droll. And dissipated so quickly. Oh well. :guinness:

 

[analag]

[quote author="Dan Kennedy"]Don't you just love geek humor, it's so droll. And dissipated so quickly. Oh well. :guinness:[/quote]

This statement makes no sense to me, am I missing something here?

 

[ruffrecords]

[quote author="analag"]How about it guys...training the newbies how to use simulators in a realistic way. Especially when using it to look deeply into tube circuits.[/quote]
I do quite a bit of tube circuit simulation but I do find the available tube models to be rather variable and also lacking in some areas. For example none of them models shot noise.

Ian

 

[tommypiper]

Is there one that runs on a Mac? LT looks to be Microsoft only...

 

[Ian MacGregor]

I poked around a bit and figured out how to represent a schematic (such as a DOA) as a symbol in a larger schematic.

You need to make sure that the name of the schematic and its associated symbol are the same. For example using a Hardy 990:

Amp Schematic: "JH_990.asc"
Amp Symbol "JH_990.asy"

The catch is that in order for this part to now show up in the "Select Component Symbol" window, it seems like the higher heirarchy schematic must be in the same directory as your lower heirarchy symbols and their associated schematics (hope that made sense). If you try this and are having problems check the "Top Directory" pulldown menu at the top of the "Select Component Symbol" dialog box. You should be able to point it to whatever directory you are working in.

Hope this helps someone.

ian

 

[12afael]

thanks Ian :guinness: :sam: :thumb: , I did a test and it work :razz:

the label net on the schematic must be the same on the symbol.
I put an .include to the schematic file and it didn´t work but without it , it work. the schematic and symbol on the same directory make the magic. :wink:

Rafael

 

[Ian MacGregor]

Ahh yes, I forgot a very important part. Each "pin" must have a net name that is the same as the symbol pin name that it corresponds to.

Thanks Rafael.

Ian