I am using an OPA241PA op amp to amplify a variety of voltages (around 0.6-3.3V input to about 4-23V output). If I have understood the datasheet correctly, this amp should be capable of accomplishing my goal. The schematic is as follows:
When 3.3V is input, the amp behaves as I believe it should and the output is about 23V. However, when the input is 0.9V, the output is around 15-16V; a gain of almost triple the intended. How is it possible that my gain changes when my input voltage changes?
EDIT: I have since found that when the 0.9V input is supplied, there is ~2.6V developed on the negative terminal of the amp. I don't know how this voltage could be present.
Link to datasheet http://www.ti.com/lit/ds/symlink/opa251.pdf
Thanks for the input, I've concluded that the problem is with my source, not the op amp circuit. Once the source was replaced the amp worked correctly.