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SPICE model import error

Posted 12.03.2019, 14:13 GMT-4 Low-Frequency Electromagnetics, Modeling Tools & Definitions Version 5.1 1 Reply

Michelle Weinmann
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Hello,

I am trying to model an op amp which changes the amplitude of the output of an LVDT that I have already modeled. The LVDT is modeled using the magnetic field physics and I have tried adding an electric circuit physics to model the op amp. There are two other electric circuit models that I am hoping to replace with this model which I have not removed yet. I imported the SPICE netlist provided from Texas Instruments who make the op amp I'm using. However, an error pops up: device FB refers to missing device POLY. I'm not sure how to rectify this error, any assistance would be appreciated. I have attached my file with the error and the TI SPICE file.

Thank you, Michelle

1 Reply Last Post 20.03.2019, 09:28 GMT-4
Dennis Brown
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Posted: 6 years ago 20.03.2019, 09:28 GMT-4

Hi,

Chances are that comsol does not know what the term POLY means in the netlist. These are an E and F source that both have that term so if you edited out the E source, chances are the F source would then throw up a flag. Example edit:

  • EGND 99 0 POLY(2) (3,0) (4,0) 0 .5 .5 FB 7 99 POLY(5) VB VC VE VLP VLN 0 4.715E6 -5E6 5E6 5E6 -5E6

See if you can simplify the spice netlist for the op amp a bit more. it just comes down to that the comsol spice feature is bare bones. If you are on support then send it in to them, maybe they have a suggestion. For a more "ideal" simulation, using just an E source with a high gain value (like 100k, 1e6, etc), and then using resistors to do usual op amp stuff should get you closer. All of the other spice netlisting are details that may or may not help. It's dependent upon what you want to know. I would leave that spice model for a program like ltspice or some other variant of spice out there.

Also, why do you have so many circuit nodes in your model? Should only need one. I did not look at your model otherwise so maybe I am wrong. My suggestion would be to get both models to run as expected separately and then combine and troubleshoot. When you do combine the simulations you will probably have to use a fully coupled solution.

Hi, Chances are that comsol does not know what the term POLY means in the netlist. These are an E and F source that both have that term so if you edited out the E source, chances are the F source would then throw up a flag. Example edit: * EGND 99 0 POLY(2) (3,0) (4,0) 0 .5 .5 FB 7 99 POLY(5) VB VC VE VLP VLN 0 4.715E6 -5E6 5E6 5E6 -5E6 See if you can simplify the spice netlist for the op amp a bit more. it just comes down to that the comsol spice feature is bare bones. If you are on support then send it in to them, maybe they have a suggestion. For a more "ideal" simulation, using just an E source with a high gain value (like 100k, 1e6, etc), and then using resistors to do usual op amp stuff should get you closer. All of the other spice netlisting are details that may or may not help. It's dependent upon what you want to know. I would leave that spice model for a program like ltspice or some other variant of spice out there. Also, why do you have so many circuit nodes in your model? Should only need one. I did not look at your model otherwise so maybe I am wrong. My suggestion would be to get both models to run as expected separately and then combine and troubleshoot. When you do combine the simulations you will probably have to use a fully coupled solution.

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