STM32L0 DAC Voltage Reference

[Throy]

I'm currently using a STM32L052K8T6 and am trying to use the DAC. I'm a little confused as to what reference voltage is being used by the DAC. When I have the output buffer disabled 4095 = 1.23v which is the internal reference voltage. When I have the output buffer enabled 4095 = 2.02v. I expected it to be 3.3v (vdda) as it shows in the reference manual.

The DAC output is being buffered by an op-amp. So there should be little current being sourced by the output.

I'll try to post my configuration code later if need be. Currently don't have internet at home and am having to post this from my phone.