Regarding I/V conversion, I have no specific knowledge of the HOLO DAC’s design beyond what has been posted and linked to here, but it seems to me to be possible that it doesn’t need any. A ladder-type D/A converter circuit, including "segmented" ladder types such as the HOLO appears to be, can be designed to provide either a voltage output or a current output from the ladder itself.
Of course in either case an analog output stage of some sort would most likely still be required. Although if I recall correctly one of the very expensive upper echelon TotalDAC designs manages to do without even that, and by using a multitude of D/A converter circuits in parallel can apparently provide adequately low impedance for many applications without having any active devices between the ladder and its output.
Regards,
-- Al
Of course in either case an analog output stage of some sort would most likely still be required. Although if I recall correctly one of the very expensive upper echelon TotalDAC designs manages to do without even that, and by using a multitude of D/A converter circuits in parallel can apparently provide adequately low impedance for many applications without having any active devices between the ladder and its output.
Regards,
-- Al