Q
I want to know what capacitive load the AD8002 output can drive, I don't findthis on the datasheet?
A
For anything over one or two pF, a series resistor is required to compensatefor the load capacitance. The series resistor produces a stabilizing zero in
the open-loop response that keeps phase margin from getting too small. Figure
7 in the data sheet indicates what value of resistor should be used for a
particular load C. I’ve pasted the figure in attachment.
I recommend that you read the section in the data sheet that refers to this
figure. This technique reduces the overall bandwidth and produces some
attenuation due to load resistance. There are several good technical articles
on the ADI website that explain how this compensation technique works, as well
as “in the loop” compensation that avoids the loss due to loading, but still
has loss in bandwidth.
Increasing the feedback resistor value also increases phase margin, and
therefore also increases the load C driving capability, but also reduces
closed-loop bandwidth.
Attachments:
