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What amp op to use to drive an FDA common mode pin?

Question asked by EVC on Oct 5, 2017
Latest reply on Oct 6, 2017 by JinoL

I need a hint on what op amp to use for U2 in the circuit below. Analog/LinearTech line card is big so I would like to pick a part that could work, have as a low power consumption as possible (< 2mA), low noise and lowest cost as well as it is a multi-channel design. Regarding noise I had assumed at first it does not need to be extremely low noise as noise tends to be canceled by system's CMMR (THS + AD) but I may be missing something. I also assumed it is not demanding as far as output impedance is concerned but again I want to make sure I did not miss anything. I am looking for a part with good PSSR rejection, even if the +5V voltage is very well decoupled and as quiet as possible.

The AD reference voltage is 5V but it will be possible changed to 4.096 so the AD VCM output may be either 2.5 or 2.0V in the final design.

THS4131 is used in the current design but I intend testing LTC6363 in the same position because of its (much) lower power consumption. Not sure if it makes a big difference to the answer but I thought it would be worth mentioning.

 

So... What parts would you suggest, AD or LinearTech?

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