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OPA810: Causes for the phase decline in high freq in 'Open-Loop Gain and Phase vs Frequency'

Kaihang Zhou
Prodigy 40 points
Part Number: OPA810
Other Parts Discussed in Thread: LM358

Tool/software:

Hi, 

I'm deep diving in op-amps. I noticed there is a difference in 'Open-Loop Gain and Phase vs Frequency' between LM358 and OPA810. And I noticed that there is only one phase decline in LM358 and two-phase declines in OPA810. I am wondering what causes the difference, is there any articles to learn about this?

Thanks!LM358 Open-Loop Gain and Phase vs Frequency OPA810 Open-Loop Gain and Phase vs Frequency

  • +1
    TI__Mastermind 18045 points

    Hi Kaihang,

    I believe the LM358 graph has zoomed in on their plot and is not showing the dominant pole, which is the first phase shift that occurs. As you can see the dominant pole starting at around 100Hz in the OPA810 graph causes the first phase shift which then flattens out to 90 degrees similar to where the LM358 starts then both graphs show the higher order poles as there is another phase shift being shown by the additional phase decline from 90 degrees.

    Best Regards,

    Ignacio