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 14 Jul 2005, 3:14 PM
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Joe
Joined on 07-14-2005
Posts 7
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connecting part with model
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Hello,
I used PSpice several years ago and got to where I could make it do anything, and then I've used Elec. Workbench for several years, and now I'm back using PSpice again under Orcad_10.3. Some things have changed since I used PSpice. I feel stupid because I'm just trying to get a simple opamp circuit to simulate and when I say 'run' I get an error saying there is no PSpice model for U1. I have followed the tutorial on PSpice and thought I had the model set up properly. I even changed my circuit to use an LM358 which is already in the library and it still could not find the model. I am baffled. I am surprised at how many places it seems I must declare that model. I know I went through some trauma learning how to set up parts and models years ago. Seems like deja vu all over again. I know this is an unfair question and I sound like a newbie which I'm not, but I am lost as to what I could be doing wronb. Anyone have any ideas?
Joe
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18 Jul 2005, 2:33 PM
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Joe
Joined on 07-14-2005
Posts 7
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Re: connecting part with model
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Al,
I think you hit on something. I did not realize that there are two separate libraries for Capture parts and PSpice parts. I was grabbing the op amp from an .olb library. The thing that is confusing is that I got a bipolar transistor from a bipolar.olb library and it had a pspice model and I was able to simulate a simple transistor amp. So I couldn't figure out why I couldn't do the same with the op amp. However, where does one search for the appropriate library? I'm not sure the help docs indicated anything to me about two different libraries.
Thanks & Best Regards,
Joe Babb
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18 Jul 2005, 2:40 PM
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Joe
Joined on 07-14-2005
Posts 7
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Re: connecting part with model
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Al,
I think maybe I found it. One is under Capture\Library\opamp.olb,
the other is under Capture\Library\PSpice\opamp.olb.
The second one has a spice model reference.
I'm setting here wondering why this should be? Same name for a different library? Shouldn't a part data base include all pertinent info on a part? Well, I suppose I should be happy that now I know. Many thanks for the help.
Joe
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18 Jul 2005, 5:33 PM
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rmann
Joined on 04-22-2002
Redondo Beach, CA, USA
Posts 1,765
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Re: connecting part with model
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Joe, Capture and PSpice are two different products.
Capture is used in two general contexts. Capture is used to generate schematics for the purpose of documenting a circuit design and/or toward designing a PC board to be used in a commercial product. Capture is also used as a front-end interface toward circuit simulation, using PSpice as the actual back-end simulation engine. It's this dual-purpose nature the accounts for the fact that there are two sets of libraries.
Something around 80% of Capture users don't need simulation, and therefore don't use PSpice. (Ok, so I made up that number, but I don't think I'm very far wrong.) For this reason, there are two separate sets of libraries available, one set for the pure Capture users and the other for the PSpice users.
Except for very large ICs, with tons of pins, it's very quick and easy to create a part for pure schematic use. You draw the graphic symbol, add pins as necessary, add some properties as needed and adjust their visibilities. On the other hand, creating a simulation model is seldom a trivial exercise, even for those versed in the science. Because of the considerable extra expense of generating the simulation models, the libraries supplied for use with just-plain Capture are lacking models - like most of us out here don't need them. And that's why you see two sets of libraries. If you had bought just Capture without PSpice, you would have been given only one, the one that includes no support for simulation.
-Richard Mann
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19 Jul 2005, 9:45 AM
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Joe
Joined on 07-14-2005
Posts 7
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Re: connecting part with model
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Hi Richard,
I understand what you are saying. However, I am one of the minority that wants to design, simulate, verify, and then move directly to layout. It seems as though I've been waiting my entire career (30 years now) to find a product that integrates that process well. I'm still waiting.
Even given your explanation, I still don't see why the libraries would be named the same and why a clear explanation of the difference in usage between Capture and Capture/PSpice wouldn't be made by the tutorials and help files. Even if most of the users don't do simulation and don't need spice models, I know from programming experience that it should be possible to integrate the data base such that a person like me could easily add the spice model to the pure Capture model. I'll get down off my soapbox, now. I really do appreciate the explanation even if I don't understand why it should be that way.
Best Regards,
Joe
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20 Jul 2005, 4:35 PM
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gsmollin
Joined on 10-17-2002
Posts 20
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Re: connecting part with model
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Joe,
Richard gave you the weak reason why there are two libraries. The strong reason is that Pspice is not an Orcad product. It was developed by Microsim at the same time Electronic Workbench was developed by I forget who. Years ago Mentor bought the Workbench, and integrated it into their design system. Orcad has not integrated Pspice, and with the acquisition by Cadence, it is even less likely to become an integrated product. You will really begin to appreciate how disjointed the product is when you try to write a new simulation model, and connect it to a part model. I have had the displeasure of doing this on several occasions, and the effort is way out of proportion to the reward. To make things worse, the documentation is byzantine, just like the product, actually.
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21 Jul 2005, 9:08 AM
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Joe
Joined on 07-14-2005
Posts 7
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Re: connecting part with model
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Well, forewarned is forearmed, or something like that. Why is it that engineers have to work with tools that are less than what should be? Ah well, I'll shut up and go back to work.
Thanks everyone for the help. I'm up and running now.
Joe
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13 Aug 2007, 5:50 PM
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JP
Joined on 08-13-2007
Posts 1
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Re: connecting part with model
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As far I'm concerned, I feel less stupid now ... because I need to simulate a filter design TOO and can not use the .cir file provided by the compagny. So ... anyone is able to help me or do I have to stay with the "capture and pspice are not well implemented" ?
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13 Aug 2007, 7:46 PM
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rmann
Joined on 04-22-2002
Redondo Beach, CA, USA
Posts 1,765
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Re: connecting part with model
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Hi, JP,
I'm not sure, but I wonder if you wouldn't be better off starting a new thread. It sounds like you have a different set of problems, although it's hard to tell because you were a little vague in laying it out. Mainly, it's not clear what you mean by not being able to use the .cir file supplied by the company. Could you elaborate on which .cir file, by which company, and what it is that you are trying to do with that .cir file. Once we get a little more to go on, I'm sure there's somebody here that can help.
By any chance, are you using "Schematics", rather than Capture, for your schematic creation?
-Richard Mann
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OrCAD Community » OrCAD Community Forums » Simulation using PSpice » connecting part with model
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