From time to time I think about building an R-2R ladder and drive it with some HCMOS buffer chip, and was wondering about resistor tolerances. It seems like the cumulative error using 1% resistors would max out at about 2%, wouldn't it? And even if you used wide- tolerance resistors, say, 10% or even 20% (there used to be such things) yes, it could be all over the map, but would it still be monotonic? The error of each lower bit is halved (isn't it?), so even if one is +20% and the rest are -20%, - hmm. Can anybody do this in their head? Would the transition from 01111111 to 10000000 go upside-down?
Just wondering...
Thanks! Rich