Can you please clarify how selection of reference buffer like AD8031 was done?

Can you please clarify how selection of reference buffer like AD8031 was done? That's an 80MHz op-amp, how will it be stable with 10uF of load

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    •  Analog Employees 
    on May 8, 2018 5:51 PM over 2 years ago

    On behalf of Ryan Curran.
    In many cases, using such a large capacitor at the output of a high speed buffer would be detrimental to the performance of the amplifier. However, this reference setup has a few things working in its favor. First is the fact that the reference signal is essentially a DC level. There are no bandwidth requirements placed on the amplifier. It only needs to maintain a single DC voltage. Second, the 10 uF capacitor so significantly overdamps the circuit that it eliminates any potential ringing or small oscillations. It’s actually a problem if the capacitance is reduced to say 1 uF or so. In this scenario, it may be possible to induce ringing. Third, the parasitic trace resistance between the buffer output and the decoupling capacitor is enough to maintain proper phase margin. For these devices, the trace resistance needs to be no more than 30 or 40 milliohms.