[sdiy] sample and (infinite) hold

[Scott Juskiw]

I've built a S&H circuit using one of those dedicated LF398 S&H 
chips. It works as expected, but I'm finding the droop to be 
unacceptable; I need a S&H with infinite hold. I searched the net and 
found a couple of references like this one:

http://www.maxim-ic.com/appnotes.cfm/appnote_number/12

which explains how to accomplish this using an ADC followed by a DAC. 
But then I looked at the prices of those ADC chips, gadzooks! I can't 
even find a source for the chips mentioned in the app note (beyond 
free samples). I'm hoping there's a cheaper solution.

Has anyone built a sample and infinite hold and can shed some light 
in my direction?