[sdiy] while we're talking about scaling & biasing etc

[Neil Johnson]

Hi,

> mc34072. i picked it because it was rail-safe.

Not specific to the MC34072, but do you have a resistor (say 100-220 ohms) in series between the output of the op-amp and the input to the ADC?  When the ADC samples it puts a small capacitor on the input, which can cause an op-amp to ring.

Better still if you also have a capacitor (e.g. 10n) between the ADC input and GND.  This minimizes the droop when the sampling capacitor (typ. a few 10's of pF) is connected.

Neil
--
http://www.njohnson.co.uk