simple sample/hold circuit?

[Haible Juergen]

	>Constancy of the update frequency is not required. 
	>
	>Bye
	> René


You mean updating the demux / S&H stages ?
The great advantage of a constant update frequency is that 
you can tolerate a little leakage (in cap, opamp, switch)
as the components are ageing. Leakage will cause
a little drop of average voltage, and a tiny ripple, but in
many cases you can compensate for that by adjusting the
respective parameter a little.
Not so with varying update frequency. I posted about this
before, so I'll keep it short, but due to a different update rate
during autotune and during  normal operation I had a *nasty*
tuning problem in my Prophet 5. Sure, replacing the leaky
opamp (talking nanoAmperes here !) cured the problem,
but it might have kept working for a long time with constant
update frequency, and finally the fault would have been a lot
easier to find.

JH.