[sdiy] sample and (infinite) hold

[Ken Stone]

Check the LM3900 app notes for the bias current canncelling arrangement.
Serge uses this for the "hold" function in his old envelope generator. As
the circuit is adjustable, you should be able to null out the droop qite nicely.

Ken

>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?
>
_______________________________________________________________________
Ken Stone   sasami at hotkey.net.au or sasami at cgs.synth.net
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