[sdiy] Some OTA questions

[Jeff Farr]

I've been working my way through the EN app. notes on the 3080 and
there are some nagging questions left, first, there is an example of a
S&H circuit where a 3080 in switch mode is feeding a capacitor with a
FET buffer.  If I understand this correctly Vdiff simply switches on
the 3080 and since Iout = Ic it's Ic that is doing the "sampling" so I
would connect my source (noise) to that.  Do S&H's usually work with a
current in?  Second, I haven't yet figured out how to make use of Id
in a 3280, can someone point me to a good app note about that?  What
about the differences between a 3*80 and one of the LM1*00 OTA's?