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TINA/Spice/OPA322: imported model not working in Cadence OrCad

PPera
Prodigy 40 points
Part Number: OPA322
Other Parts Discussed in Thread: TINA-TI,

Tool/software: TINA-TI or Spice Models

Hi everybody,

I'm new to this forum, so please feel free to correct me if I'm making mistakes.

As the title suggests, I'm currently trying to simulate a design containing the OPA322. I downloaded the model from TI website and followed all the instructions contained in Application Report SLOA070 ("Using Texas Instruments Spice Models in PSpice"). I found that the when running an AC sweep simulation, the results are not correct. To better explain what I'm telling you, I implemented a very simple design, that I attached, which is a basic circuit with an OPAMP in non-inverting configuration (schematic.jpg).

If a run a transient simulation, using a sinusoidal waveform as the input (0.5V amplitude, 200Hz frequency), the output voltage is what I expect (transient.jpg). If i run an AC_sweep simulation, the results does not make any sense (ac_sweep.jpg) (I would expect an output of 0.5V in all the pass-band). Looking at the transient simulation I've seen that there is a small glitch at startup (transient_detail.jpg), but I do not know if this has something to do with the weird result.

I've also tried to use TINA simulator, but with that tool everything worked fine. The only problem is that I have to use Cadence OrCad, so I need the model to work with this simulator.

Thank you in advance

Pietro test_opa322.zip

  • 0
    TI__Intellectual 2680 points

    Hi Pietro,

    The attached project behaves as expected in AC simulation and gives the below output when tested in PSPICE in 16.6 [16.6-S086(v16-6-112HJ)].

    Please note that, during AC simulation PSPICE doesn’t consider amplitudes of trans sources entered. It will consider the amplitude that is entered in ‘AC’ option of the Vsin source and compute the gain on that. (see fig plot of V(v_input))

    All other trans and dc sources is considered 0 in AC scale ( see fig plot of V(IN+)).

    The gain of the configured circuit is -1 (inverting configuration) and given ‘AC’ =1, it considers 1V AC signal at all frequencies.

    Based on that output gain should be -1, which means, magnitude is 0dB or 1V/V and phase should start from 180d in Bode plot which is also seen from the validation result.

    Regards,

    Saket

  • 0 in reply to Saket
    Prodigy 40 points
    Hi Saket,
    I think it was a problem of installation. Every time I launched the simulation, I ended up with -44 dB of gain in what I would expect to be the passband... which did not make sense to me.
    I uninstall and re-install the software and the weird behaviour disappeared. Now the bode Plots look like yours.

    Regards,
    Pietro