I'm using a unity gain buffer to drive a power amplifier voltage reference. Here's a schematic for the buffer configuration.
The op-amp in question is a LMV321.
I've set the voltage divider at the amplifier's non-inverting input to output 2.85V. Unexpectedly, I'm measuring the voltage at the inverting input and output as between 2.70V and 2.75V (it changes somewhat which I'm also surprised by). The measured non-inverting input voltage is stable at 2.854V. As you can see from the schematic, the supply voltage is 3.3V (3.28V measured). When the device is off, I measure the DC resistance between the output and ground as \$2.328k\Omega\$.
The max input offset voltage specified in the datasheet is 9mV, not the more than 100mV I'm getting. I've kept the output voltage well below the 3.3V supply (especially considering this is a rail-to-rail op-amp).
The load is the a reference input voltage of a SE5004L power amplifier, which is supposed to be supplied with a voltage between 2.8 and 2.9V. I'm having a little trouble determining what the input impedance of that pin should be although I guess it has to be about 2.328k (op-amp output impedance in parallel with it, which is so high that my multimeter reads OL when attempting to measure the resistance). I unfortunately don't have an extra power amp to measure the impedance, and I'd rather not have to take it off and resolder it. Please let me know if I've omitted relevant information.
Any thoughts on what might be going wrong here?