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ADA4075-2 PSRR decreasing during operation?!

Question asked by Adex on Jan 26, 2017
Latest reply on Jul 18, 2017 by krisf

Hello,

 

I have got an amplifier which is working pretty well with ADA4004-2, OP284 & AD8599 Low Noise OA's.

Please see schematic attached, it has two +/-5V supply lines.

 

ADA4075-2 is 3-4 times cheaper, so it is more attractive on that reason

Unfortunately, my two attempts do replacement failed.

 

First time after replacement ADA4075-2 is working as expected - I able to see 50Hz theed-through in spectrum only.

But, after several outputs of operation, harmonics starts to be seen.

 

I suspect that PSRR decreasing drasically, as far I have small disturbance on PS line, caused by DC-DC.

 

Please advise.

 

Best Regards,

Konstantin

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