[sdiy] Servo / Hold?

[Czech Martin]

Bob Pease made a nice write up about that.
He showed how to compensate for leakage and 
for soakage. Unfortunately this circuit
relies on capacitor "matching" in
terms of soakage, so I think it will need some time
of experimentation until the circuit works.

http://www.national.com/rap/Application/0,1570,28,00.html

The best thing would be to avoid soakage at all,
using better caps, but I have never seen a teflon
or glas type. They seem to be not available for DIY.
Even those have some soakage. The integrated MIM
caps in CMOS ICs are close to perfect...

m.c.

-----Original Message-----
From: Tim Parkhurst [mailto:tparkhurst at siliconbandwidth.com]
Sent: Mittwoch, 12. Februar 2003 19:29
To: synth-diy at dropmix.xs4all.nl
Subject: [sdiy] Servo / Hold?


Hi All,

Just a real quick idea that I wanted to bounce off the group: I was trying
to think of some sort of feedback circuitry that would act like a servo (or
a DC PLL I guess) that could compensate for the droop in a S/H capacitor. Is
this possible, or would it cause more problems than it would solve? Has
something like this been done before? Perhaps there could be a circuit in
the feedback loop that would output a voltage proportional to the amount of
change in the 'stored' voltage (and therefore compensate for the droop). Of
course, it sounds like this feedback circuit would use capacitors to store
charges and so becomes another S/H itself (which defeats the whole purpose
of the thing). Maybe it would be easier to just do it digitally... ;)

Any thoughts?

Tim Servo
"Imagination is more important than knowledge." - Albert Einstein
 




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