DAC Offset Compensation

[bitshift]

Hey guys,

I'm using a Microchip 12 bit DAC (MCP4921) in a project I'm working on. I'm using a 2.048V reference to give an LSB of 0.5mV.

It's working great but according to the datasheet, the DAC has an offset error of 1% of the full scale range. With the 2.048V reference this can be roughly as high as 21mV. In practice I've measured an offset error of about 1.5mV.

The output of the DAC goes into a voltage follower. I then use the following circuit to compensate for the offset voltage of the op amp:



So my question is, how do I compensate for the offset voltage of the DAC?

[SeanB]

Set an output of 0V, then adjust pot for that voltage. Simple enough, though you probably will want to have a gain trim as well for the full scale as well, either by having a small offset on the reference or a adjustment on the DAC. Even more tricky is having a bipolar output and adjusting for that to be monotonic and equal for both full scale values.