I want to add a DC volatage of 1.25V to a sine wave signal. I am using a DC bias circuit with a voltage divider (R1=R2=100Kohm) connected to a 2.5V source and to the ground. That is giving me the correct 1.25V DC offset that I need in my application.
However I would like to lower the impedance so I am using a voltage follower op amp. I am using the LT6202 op amp which is supposed to be rail-to-rail and unity gain stable. When I connect the voltage follower to the DC bias circuit I mentioned above, the DC offset rises from 1.25V to 1.32V.I have done the simulation also and I am getting the same results.
When I am using R1=R2=10KOhm instead of 100KOhm the DC offset becomes 1.258V, which is closer to the wanted 1.25V value.
I am not sure what is causing that. Any help?