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My question concerns the AD8138, one of my co-workers recently found out that this isn't a true differential amplifier, but consists of two single ended amplifiers to form the differential.  If this is the case, how is the return current handled, as there

Question asked by ddurachk on Aug 12, 2016
Latest reply on Aug 12, 2016 by harryh

My question concerns the AD8138, one of my co-workers recently found out that this isn't a true differential amplifier, but consists of two single ended amplifiers to form the differential.  If this is the case, how is the return current handled, as there is no ground pin on the device.  Can you confirm that this isn't a true differential device?  Also, how is the return current handled at the output of the device?

 

I am using two AD8138's to feed a 2-channel differential ADC (ADC12D1600).  We are seeing some crosstalk between the channels, and believe we've ruled out any possibility that the ADC is responsible for the problem.  The ADC12D1600 has a common mode reference that it provides to the front-end circuitry, and in this case it is feeding both common mode inputs of the 8138's.  Could this pose any problem (the common mode pins of both 8138's are shorted together.)

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