long time S&H / integrator question

jhaible jhaible at debitel.net
Mon Mar 13 11:48:54 CET 2000


Hi,

I was thinking about S&H / integrator configurations,
the choices being

a) capacitor to GND, opamp buffer (MOSFET inputs)
b) inverting opamp integrator (same opamp), capacitor
in feedback configuration.

Same switch to disconnect the capacitor from the driving
source, or the opamp summing node from a current source.

I would highly prefer option (b) for a certain application,
and I was wondering if there are any disadvantages
in terms of leakage. ((a) would have a guard ring powered
by the follower output, and (b) would have a GND guard ring.)

Is there any reason why (b) should loose voltage faster than
(a), when the switch is open ? Anything else that speaks agains
option (b) ?

JH.





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