Problem  voltage follower AD8548 & ADA4891


Currently i am doing a test PCB in order to simulate a wide range of thermistors sensors. I generate a voltage with a DAC (TLV5630) and then jus to protect the DAC i use a amplifier as votlage follower.

First of all i used AD8548, but I found with a problem because, when i put 5V in the output of DAC i had 5Voltage but after the voltage follwer i had 4.86V. Looking more accurate datasheet i though it could be due to the maximum output current. And I decided to change by ADA4891 that seems it could supply up to 4.4mA and it seems would work well.

Today I tried the new amplifier but i still have the same problem, and i don't know why that's happen.

The other point is: if i put the output of DAC directly it seems work perfectly (no voltage follower).

Anybody has experience in that field, and Would you mind help me on this?

Here bellow i atacch the schematic.