Hello All

        I want to incorporate a simple resistor-based DAC within a
PIC application. I have in mind using an R-2R ladder, either directly
on a PICs port pins, or (for other reasons) via a latch, and then to
an op-amp buffer etc.

I realise that there are limitations to this approach, but certainly in
terms of speed, it should be adequate for my application. Has anyone any
experience in improving the accuracy of this basic arrangment? I am
thinking
in terms such as:

        - Voh and Vil levels and variability for the PIC/latch (logic family?)
        - loading of the port pins
        - resistor tolerances
        - modifications of the simple R-2R ladder, alternate weightings etc.


        Any suggestions gratefully received.

        Best Regards
        jon Nicoll