Dave Tweed wrote: > A 1-bit network gives you 2R or 1R. > A 2-bit network gives you 3R, 2R, 1.2R or 1R. > A 3-bit network gives you 4R, 3R, 2.2R, 2R, 1.33R, 1.2R, 1.05R or 1R. > A 4-bit network gives you 5R, 4R, 3.2R, 3R, 2.33R, 2.2R, 2.05R, 2R, > 1.43R, 1.33R, 1.23R, 1.2R, 1.08R, 1.05R, 1.01R or > 1R. > > As you can see, each additional switch puts twice as many values into > the lowest 1R span of resistance values, and even at just 4 switches, > you need to be able to distinguish values that are as little as 1% > apart. There's no straightforward way to "linearize" this. Yeah, I just worked it out too and I can see that a R-2R ladder doesn't wor= k for resistance after all. Sorry for the confusion. ******************************************************************** Embed Inc, Littleton Massachusetts, http://www.embedinc.com/products (978) 742-9014. Gold level PIC consultants since 2000. --=20 http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .