OPA197-Q1: Output Impedance of OPA197-Q1

See figure 6-18; the slope is approximately 40 Ω at 25 °C:

Hi Manoj, 

Please see the curve below for the output impedance of the OPA197-Q1

Best Regards, 

Chris Featherstone

The voltage drop becomes noticeable only when you try to drive an output voltage near the rails. As shown in figure 6-18, when sinking 10 mA, the output can go only about 0.4 V near V−.

The opamp's internal resistance is part of the feedback loop, so it is regulated away. There is a voltage drop of exactly 4.5 V between the supply and the output. The offset between the desired and the actual output voltage is at most 250 µV.