Vector Imagery

[Lee Davison]

> What I really would like to find is a formula for calculating R2R
> ladder values so that I could get a 0V-5V output from an 8-bit
> parallel port.  Constructing it is easy, once one knows what
> resistors to pick.

The output impedance of an R2R ladder is R so you chose R to suit the
stage the ladder will drive. You won't get 0V-5V without some sort of
amplifier on the output, even using CMOS gates to drive the ladder.

For a more monotonic output 2R should really be 2R-Rout where Rout is
the output impedance of the driving gate.

Lee.