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How to predict current usage of multiple op amps

Question asked by m3atwad on Apr 4, 2016
Latest reply on Apr 4, 2016 by harryh

I have multiple op amps (AD8237, ADA4661, ADA4500) all tied together serially so one feeds the other and the last one drives the ADC.  I know the AD8237 is an instrumentation amp, but I thought since the rest weren't this was the right place to post. 

 

I see the quiescent currents in the data sheet, but how do you predict how much current they will pull when operating.  Each one drives the input to another amp until this last one which drives the adc.  I know all the design stats like they are powered by 3.3V, two of them can apply a gain up to 10, I know the expected input signals, I know the voltage dividers for the different gain values.  I'm just not sure how to use this information to get a rough idea of how much current they all might pull.

 

This has come about because I'm trying to run this analog section off of a voltage reference that can supply up to 20mA.  This would be ideal because I could tie the analog chips and ADC to the same high precision voltage reference.  I'm just worried about exceeding my current limit of 20mA.

 

Any advice/direction is appreciated.

 

 

Rob

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