AD8510 and capacitive loads

Steffen,

  With 5 ohms and 2 nF, you have a pole at about 15 MHz which will give you some phase shift, etc.

Op amps are not perfect voltage sources with zero ohm output impedance, so all op amps have

trouble with cap loads, it's only a matter of degree.

  The only way you have a chance is with a bigger Rs.  Close the loop for DC at the cap load,

and close the loop for AC before the resistor.  See the last schematic in:

http://www.analog.com/library/analogDialogue/archives/31-2/appleng.html

(The + and - inputs are mislabeled)

For snubber compensation, it relies on dropping the gain quickly before the phase has shifted too much.

This is most effective with op amps that have high output impedance, such as CMOS rail to rail outputs.

but is somewhat useful with bipolar RRO.

Obviously, it should not make any difference with a series circuit, but I had a customer last year that

said it did.  We did not explore.  Could have been stray C.

Harry

Dear Harry,

I have a question to the "in-the-loop compensation scheme" you proposed. This compensation method is described in figure 3 of the following article https://ez.analog.com/message/82888#82888

But how to use this compensation method in a unity gain configuration with an infinite R_IN?

Due to R_x=R_0*R_IN/R_F this would lead to an infinite value for R_x.

Regards,

Steffen

Steffen,

  I missed the fact you are connected as a buffer.  One of the designers here said a snubber is the way

to go;  values on the data sheet.

Harry