LTspice ADA4528-2 time vs frequency, response conflict

As you can see we have excellent frequency response:

but time response is really not acceptable:

Why this has been happened?

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  • 0
    •  Analog Employees 
    •  Super User 
    on Jan 24, 2021 12:20 AM in reply to mohammadsdtmnd

    Hi  mohammadsdtmnd,

    Yes, that's correct.

    I eliminated the 1/2 of circuit connected to the non-inverting input of ADA4528-2. That portion has no effect on the Loop Gain or Phase Margin and won't affect stability at all because it is not involved with the feedback path.

    Regards,

    Hooman

  • Hi again

    I've just confused, when the simulator tells that everything ok, or the frequency analysis is perfect, there is no spike in anywhere. why time response has got wrong. when phase at 7khz is 0 the output must amplify the frequency but you can see that is is bounded to certain nice value. Academically and intuitively why the response goes wrong?! Edit: I have seen spike in case when we use open loop technique but this is not our actual case.

  • 0
    •  Analog Employees 
    •  Super User 
    on Feb 4, 2021 8:58 PM in reply to mohammadsdtmnd

    Hi again,

    I've seen this before where AC response simulation may indicate all-is-good with a circuit whilst transient simulation says otherwise. There may be clues in the otherwise "good" AC response as well, but I'm not an expert to know and identify those. So, I always perform both these simulation which of course is still no-guarantee that the final circuit is perfect either. Bench characterization is essential in spite of simulation.

    Regards,

    Hooman