Digital to Analog Conversion

See:

Don Hyde says:

An R-2R ladder can be used to turn a group of [digital] output pins into a DAC for a few cents. Below is a 3-bit DAC. Using 3 [digital] output pins (beware of the odball open drain pins, they're no good for this), this circuit will provide 0 - Vcc*(7/8) volts out, with a 2R source impedence.
It can be extended to more bits by replicating the MSB R-2R end of the ladder.
Up to 4 bits can be achieved with 5% resistors.
Up to 6 bits can be achieved with 1% resistors.
...
In many applications, it would be advisable to buffer the output with an op-amp.
A circuit like this can achieve waaay higher output frequencies than PWM, and can be easier to filter, at the expense of using up a bunch of pins.
OUT o--+-/\/\/\/\----o MSB
       |    2R
       \
       /
       \ R
       /
       |
       +-/\/\/\/\----o Middle bit
       |    2R
       \
       / R
       \
       /
       +-/\/\/\/\----o LSB
       |    2R
       \
       /
       \ 2R
       /
       |
      ---
      ///

PICList Thread '[EE]: high res DA challenge'

Also:

RS-232 / I²C-Adapter & Parallel I/O Module

See also:

http://www.beis.de/Elektronik/DeltaSigma/DeltaSigma.html a delta sigma converter, which was invented by Philips in the 60's+
http://www.doc.ic.ac.uk/~ih/doc/adc_dac/ A-to-D and D-to-A Conversion via the IBM-PC Parallel Printer Port
http://www.hut.fi/~then/circuits/dacs.html Tomi Engdahl's Digital to Analogue converter circuits

file: /techref/io/d2a.htm, 2KB, , updated: 2007/2/20 20:17, local time: 2008/7/4 08:46,

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