[sdiy] 3/4 bit A/D converter (was: Sample&Hold thoughts)

[Grant Richter]

For an example of how to use an LM3914 as comparator string, see:

http://www.musicsynthesizer.com/DIY/Grant/CVtwister.html

the trick is to power the LM3914 from a negative supply. That way the open
collector outputs become current sources that can be summed with an op-amp.
You can leave out all the dithering stuff. And the pots can be replaced with
fixed resistors going to the summing node.

> The comparator string used to be call a "thermometer" circuit. Now I suppose
> it is a "bargraph" circuit. You can use one or more CD4582 priority encoders
> on the output to make a X bit flash A/D (maybe 100kHz bandwidth). Pretty
> cheap, sorta fast.
>