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Removing offset in IA AD8253

Question asked by andrea.mariscotti on May 24, 2012
Latest reply on Jun 1, 2012 by ScottH

AD8253 is a very good device, large bandwidth, low noise, but with an incredibly large offset VOS, specified as 150 + 900/G [uV].

My application is a very low distortion, moderately low noise amplifier inside a multi-channel acquisition system, This device was the right compromise.

Do you have suggestions for the correction of this offset? My considerations are:

1) the usual circuit for VOS correction (consisting of a potentiometer between a positive and negative reference, either analog or digital, and a series high value resistor to decouple it) cannot be used not to worsen noise performances and CMRR

2) can the REF input be used for this? of course driven by a low impedance source of signal, like an additional OpAmp

3) can I correct the offset at a later stage, such as a buffer or a filter? this VOS is large and the IA gain can be high [ (150 uV + 9 uV)*100 = 15.9 mV at output for G=100 ]; this means to operate the IA with a large offset: is it detrimental for its electrical characteristics, such as the THD, linearity and so on?

thank you

andrea

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