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OPA328: OPA328 TINA model Aol response oddity

Michael Steffes
Guru 48395 points
Part Number: OPA328
Other Parts Discussed in Thread: OPA134

I was looking for a newer part to illustrate some SSBW vs Gain issues, the OPA328 Aol phase, if I add that 20pF load, looks about right, 

However, if I remove that 20pF (as would be a normal practice), the simulated phase looks quite wrong - seems the modeller was really depending ont he Zol and that 20pF to get the phase right. That 20pF load will not always be there, so seems like the model could use some tuning - can't use this model for what I was trying to do. Here, without the 20pF the Aol phase barely moves off of 90deg, don't know any parts like that. 

  • 0
    TI__Genius 12955 points

    Hi Michael,

    Yes I see the same thing, and verified the phase continues to roll off for other devices with no load.  I would have still expected a roll-off from the load pole even at no load, the parasitic capacitances should still create a load pole.  Agreed this is unusual, let me sync. up with the team and see what the story is.

    Regards,
    Mike

  • +1 in reply to Michael Hartshorne
    Guru 48395 points

    Of course correct Aol phase is kind of useful for phase margin work, I am back to the OPA134 as a better vehicle for illustration.