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InAmp better than DiffAmp for interfacing to ADC?

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cupoftea

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Hi,
In the attached, surely a InAmp would be better?.....better rejection of CM noise?
 

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The questions is answered with an error analysis of the entire signal path
including A/D.....


Regards, Dana.
--- Updated ---

For just the G element I think you will find similar CMRR of IAs and Full Differential amps :



Regards, Dana.
 
Last edited:
Hi,
In the attached, surely a InAmp would be better?.....better rejection of CM noise?
1) Define "better"
2) An instrumentation amp IS a type of differential amp, with a high input impedance.
3) CM noise rejection: Look at the data sheets.
 

As noted, a comparison of the data sheets' common-mode rejection will give you the answer.
Note, that an InAmp may have a fixed gain different from what you need.
 

Many InAmps now with single R G setting R's, so manageable.


Regards, Dana.
 

Any old instrumentation amp may not be what you need,
some ADCs want really stiff drivers to tamp down kickback
noise and such. More a high speed thing as I make it out,
but I'd take ADC mfrs' hints about well mated front ends.

DC CM vs HF CM is another point to ponder. Fewer options
if you're really after high frequency (conducted susceptibility
testing or whatever).
 

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