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  • TI Thinks Resolved

OPA313: Interaction between OPA313 and OPA316 pspice models

Intellectual 860 points

Replies: 8

Views: 60

Part Number: OPA313

Current issue is that I am comparing some circuits using OPA313, OPA314, and OPA316 pspice models.  If I simulate identical circuits using OPA313 and OPA314 in the same schematic, I get results as I would expect.  As soon as I add an OPA316 to a copy of the circuit, the OPA314 response but the response of the circuit with the OPA313 drops to a much lover output voltage and longer time constant.  This interaction only seems to affect the transient analysis as the AC analysis is fine.  I didn't check noise.  I have checked to make sure there are no nodes in the schematic with common names so I'm not accidentally linking the copies of the circuits. 

I have seen behavior like this with various models over many years and in different simulators (Pspice, Multisim, and LTSpice) and always assumed there was something in the macromodel that was referencing a common node, likely ground.  I started to compare the OPA313 and OPA316 models and they share a lot of common names and also reference node 0, but this isn't uncommon in other models.  The OPA314 model shares many of the internal names and doesn't exhibit this problem.

The other odd thing is that it is only the OPA313 response that is changed.  The OPA316 response is the same regardless of if there is an OPA313 in the simulation or not.

But I decided to ask to see if anyone else has had the problem and knows of a simple solution.  I like having the models in the same schematic so I can contrast the response differences (it's a teaching application).

I appreciate any suggestions or insight.  I really need to get out of the house on a Saturday :)

Tim

  • Hi Tim,

    can you share a schematic or a TINA-TI simulation file?

    Kai

  • In reply to kai klaas69:

    LTSpice circuit is below.  It's a pseudo-charge amplifier AC coupled to a detector modeled by R4 C7 and the signal is an 80 fC charge injected via the 1pF cap.

    Interestingly, I just set up the amplifiers as simple inverting amps and there is no interaction.  That makes me think it is something in the circuit topology itself, not the macromodel.  But the odd part is if the amplifiers are OPA313 and OPA314, the simulation is fine.  Only when the OPA316 is present does the OPA313 response break.  The OPA314 response is unaffected when the OPA316 is present.

    OPA313 w/o OPA316

    Response with OPA316 present

  • In reply to Tim Sobering41:

    Oops...it didn't save the images...give me a minute...

  • In reply to Tim Sobering41:

    Trying again...

    Schematic

    Without OPA316

    With OPA316

  • In reply to Tim Sobering41:

    Hi Tim,

    when using TINA-TI, I cannot see a change:

    2063.tim_opa316_2.TSC

    6675.tim_opa316_1.TSC

    Kai

  • In reply to kai klaas69:

    Kai,

    Thank you for taking the time to look at this.  I downloaded  TI Pspice and I'll try that also.  I have not checked yet but in the past I have noticed that Tina models are sometimes different than Pspice models.  I'll try to update this when I check it out.

    Thanks again for your time,

    Tim    

  • In reply to Tim Sobering:

    You are welcome :-)

    Kai

  • In reply to Tim Sobering:

    Hi Tim,

    Thanks for your question.  I also recommend you try TINA-TI or PSPICE for TI to simulate our parts.  Our models are built for those simulators and we don't model things in LTSPICE.  So we can't guarantee that the models will work appropriately in that software.

    Regards,
    Daniel

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