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Front-End Amplifier and RC Filter Design for a  SAR ADC

Question asked by henrique on May 31, 2017
Latest reply on Jun 20, 2017 by JinoL

Hi, I'm using an Instrumentation Amplifier AD8226 followed by and RC Filter to drive an unbuffered SAR ADC. The signal to be sampled is quite slow, 1KHz with a 3Vp max. I read this Analog Design's article and i got very confused if i can use the circuit i design to perform the sampling and i really need some help.

 

The Acquisition time of the ADC is 2uS and its maximum source impedance is 1K ohms.  Doing the math stated in the article  i get  the time constant  of 356nS.  I have two questions, is this the minimum or maximum time constant  i  need to respect and can i use a filter with this time constant between the AD8226  and the SAR Adc.

 

Thank you. 

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