[sdiy] MAX SPDT swithces

[René Schmitz]

Aaron Lanterman wrote:
> Oh, wait, here's a gotcha. Only seems to be at Digikey, and they want 
> $5.78 for an SOIC version. Grrrr.
> 
> Back to drawing board. Just wanted to share my pain.

Well, and now you see why I often resort to the most widely available 
ICs, sourcing all this stuff can be a real pain.

> Maybe DG403? 50 ohm resistance. I have no idea how low we should be 
> trying to go to build a triangle VCO.

You need to ask another question.
The question is how large do I have to make the other resistors until 
the series resistance doesn't play a significant role. (With resistors 
in ~10k range the influence of the delta Ron (which is the important 
spec here) practically vanish.)
As it is, the switches resistance is no problem as long as it is 
constant, and the load is constant. You could in the end trim out small 
differences by makeing one of the references slightly trimmable. Trim 
out for maximum triangle symmetry, thats why you want two identical 
switches in the first place.

Cheers,
  René

-- 
uzs159 at uni-bonn.de
http://www.uni-bonn.de/~uzs159