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spice model of LT1363

Hi! I try to simulate a circuit using operational amplifier LT1363. For Draft3.asc, I insert LT1363 directly from LTspice library. The result is shown in Draft3.raw. While for Draft4.asc, I get the spice model of LT1363 from ADI website and import it into LTspice. The results is shown in Draft4.raw. Clearly, the currents in R3 in the two figures are different. I am wondering why this happens and how to solve this issue. Is there any discrepancy between LTspice library and spice model? Thanks.

  

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  • Your circuit is invalid.  Op amps are always operated closed loop. You are operating it open loop as a comparator.

    The spec table guarantees 70 short circuit current and 50 mA if the output is 7.5V away from the rails.

    LTSpice has models built in.

    Evidently, the model was updated.  I suspect the newer model in inside LTSpice.

    Harry

  • Hi Harry, according to my understanding, as long as the spice model is exactly equivalent with the build-in library of LTspice, the simulation results for a specific circuit should be exactly the same. No matter whether the circuit is valid or not, at least we should to get the same results.  

  • Yes, you are correct, if the models are the same, then any spice engine should give the same results.

    However, having worked at ADI, after the merger, I can say that the LT Spice guys took some of the models that

    were on the web and improved them before putting them into LTSpice.  And the web site was not updated.

    So you are seeing two different models.

    As a separate problem, what do you really want?  A high speed comparator?  Then don't use an op amp.

    Harry

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  • Yes, you are correct, if the models are the same, then any spice engine should give the same results.

    However, having worked at ADI, after the merger, I can say that the LT Spice guys took some of the models that

    were on the web and improved them before putting them into LTSpice.  And the web site was not updated.

    So you are seeing two different models.

    As a separate problem, what do you really want?  A high speed comparator?  Then don't use an op amp.

    Harry

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