[sdiy] op amp directly connected to ADC

[Chris McDowell]

I don't think capacitance on the rails of the op amp will keep the output from spiking when the internal mux changes. The scope confirms this is certainly -happening-, but it's not clear to me if it actually affects the sample accuracy, or generally "matters" beyond creating unneeded transients. 


>> my understanding is that you want to keep the thing driving the ADC input as
>> low impedance as possible in order to minimize the time...


this was my understanding as well.


Chris McDowell
ATXLED <http://www.atxled.com/>





> On Jul 29, 2019, at 1:02 PM, mskala at ansuz.sooke.bc.ca wrote:
> 
> On Mon, 29 Jul 2019, Vladimir Pantelic wrote:
>> my understanding is that you want to keep the thing driving the ADC input as
>> low impedance as possible in order to minimize the time to charge the internal
> 
> Well, that's the point of including the capacitor, which will have a low
> impedance at the relevant frequency.  Seems to me that it'd make more
> sense to put that capacitance on the op amp's power supply pins, though.
> 
> -- 
> Matthew Skala
> mskala at ansuz.sooke.bc.ca                 People before tribes.
> https://ansuz.sooke.bc.ca/
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