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#1 Jan 10, 2021
Last seen: 6 months 3 weeks ago
Joined: 2021-01-10 12:56

NOT gate simulation


I'm trying to simulate a NOT gate 74LS04 (DC sweep) in order to see the analog output voltage but I guess that a complete analog model is not included in the library. Then I decided to download the Pspice model available from Texas Instruments (Spice model option):

I convert the file to .olb following this video​ 

everything seems ok but simulation is not working

* source NOT_TI
V_V1         N00075 0 5Vdc
R_R1         0 N00400  1meg TC=0,0 
V_V2         N00234 0 0Vdc
X_U1         N00400 N00234 N00075 0 SN74LS04 

**** RESUMING 1.cir ****

ERROR(ORPSIM-15108): Subcircuit SN74LS04 used by X_U1 is undefined


Any idea about how to fix that?

thanks in advanceNOT.jpg

Tue, 2021-02-02 03:06
Last seen: 2 weeks 5 days ago
Joined: 2021-01-21 05:38


This error message appears when PSpice is not able to find the subcircuit model definition in its search path. To fix this, we need to make sure that model file being used by parts is defined in the configured libraries (.lib files).

So first, make sure that you have configured the library file. For this;

   1. For Cadence installation libraries: In Capture, choose PSpice — Edit Simulation Profile. Select the Configuration Files tab and then select  Library. Check if nom.lib exists in the configured files section. In case not, click Browse for Filename and go to the location             <CDS_INSTALL_DIR >\tools\pspice\library\nom.lib. Click Add as Global and then OK.

   2. For user defined vendor models: In Capture, choose PSpice — Edit Simulation Profile. Select the Configuration Files tab and then select Library. Browse to the location where the model is saved and click either Add to Design or Add to Profile. Click OK.

Now, if you are getting error even after adding libraries then first quick check is to make sure that .lib files are placed at writable location. It is needed as PSpice needs to write index files for the libraries.

Still if PSpice is unable to find the subcircuit in the configured libraries then check for following:

Double click on the part, for which you get error, to open Property editor. Here find the property ‘Implementation’ and note its value.

It is the value of implementation property by which PSpice searches for subcircuit in the libraries. So, open the .lib file in a text editor and find the model definition of this part and make sure that name of subcircuit and value of implementation is same. You can either change the value of implementation in schematic or name of subcircuit in .lib file.

Changing the in the schematic only resolves the problem for this current design. To permanently fix the issue, you can change value of implementation on this pat in the Capture library (.olb file) or correct the SUBCKT name in .lib file.



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