OPA2170: Open loop output resistance

Cafain,

Since you're asking about 0Hz, I think you're likely more interested in the closed-loop saturated output resistance which will determine how close the output can swing to the rail.  There are a few guaranteed output swing vs. output current specifications in the datasheet which I've copied below.  While sourcing/sinking 1mA the output will not be more than 115mV/70mV away from the rail as given in the swing from positive/negative rail specifications.  Also over the full temperature range with a 10k load and a +5V supply the output will be within 30mV from the negative rail and 50mV from the positive rail.  The typical output voltage vs. output current graphs can help you predict typical output swing for the full range of output currents.

Keep in mind that these specifications are based on a saturated output stage which will result in high levels of non-linearity and reduced open-loop gain.  As given in the final output voltage swing from rail specification in order to have an open-loop gain >110dB the output will need to be at least 350mV away from each rail with a 10k load.

Cafain,

This is how.

Gain defaults to a dB scale. ZOUT = 10^ ([left side flat gain]/20)

You may also right click gain scale and change to linear scale which also shows the maximum value (100.015ohms)

I do not have a range, but I use you that the variation in Aol  (110dB min, 130dB typical, estimated 150dB max) is +/-20dB will have a bigger effect on the required input change to support 0mA and 5mA.

5mA change across ZOUT of 100 ohms is 5mA * 100 ohms = 0.5V.

If AVD is 110db, input change is 0.5V/110dB = 1580nV

If AVD is 130db, input change is 0.5V/110dB = 158nV

If AVD is 150db, input change is 0.5V/110dB = 15.8nV

At this point is this, give the customer the result from Collin's and my efforts.