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AD8475 CMRR

Question asked by Crowbar on Jan 29, 2015
Latest reply on Feb 2, 2015 by Crowbar

Hello!


Correct me if I’m wrong. I want to estimate an error on AD8475B output caused by its finite CMRR. Let’s assume that AD8475 is powered from 5V supply (-VS=GND, +VS=5V) and is connected to an ideal voltage source in SE configuration and a gain of 0.4 (just like on datasheet page 21). Let –IN 0.4x =GND and +IN 0.4x = 10V. Taking into account 5V supply, the AD8475 CM bias (not the VOCM) is a half supply = 2.5V, so our signal has a 2.5V common mode component referred to CM bias. AD8475B CMRRmin=86dB so an output voltage error related to an input 2.5V common mode voltage will be ~ 125uV.


Am I right calculating input voltage common mode components related to AD8475 half supply bias?

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