[sdiy] DIY Parallel DAC

[Simon Brouwer]

Op 31-7-2011 19:59, David G Dixon schreef:
>> You can drive an R/2R ladder from a CMOS buffer or a register
>> such as 74HCT377. Make sure the IC has its own well
>> decoupled/stabilized voltage rail and use large resistors
>> (50..100k or so) to minimize the influence of the output
>> resistances which can be up to ca. 70 ohms. With some 0.1%
>> resistors for the most significant bits you could get around
>> 8 bit accuracy.
> ...or use the smaller resistances but drive the ladder with a unity gain
> buffer.

Um, no. The ladder in an R/2R DAC is not driven with a single analog 
voltage, it's driven with multiple digital voltages (by "CMOS buffer" I 
mean a multi bit buffer IC such as 74HCT240).
See 
http://en.wikipedia.org/wiki/Resistor_ladder#R-2R_resistor_ladder_network_.28digital_to_analog_conversion.2C_or_DAC.29

-- 
Vriendelijke groet, Simon Brouwer.