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AD8475 introduces too much noise, any suggestions?

Question asked by OliverSedlacek on Jul 17, 2013
Latest reply on Jul 17, 2013 by OliverSedlacek

I'm driving an LTC2440 24 bit sigma delta ADC with an AD8475 funnel amplifier. If I short the ADC inputs together I measure about 7 counts RMS noise, which is about 2uV RMS. This matches my expectation and the figures quoted on the ADC datasheet for a system with a 10Hz to 1kHz bandwidth. My problem is that when I drive the ADC through the AD8475 I measure 105 counts RMS of noise, which is over 25uV RMS.

 

Can anyone suggest a way of improving on this?

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