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PROBLEM-AD5545 AMPLITUDE DECREASING AT HIGHER FREQUENCY

Question asked by Jagadish on Jul 21, 2011
Latest reply on Jul 29, 2011 by LiamR

Hi,

 

         We are using the DAC AD5545  in Bipolar mode 4-Quardant as per the specified figure:22 in the Datasheet.In that we have used an OP-AMP AD8512 instead of datasheet specified OP-AMP .

 

       We are facing the problem In Analog output Amplitude at Higher frequency. The Amplitude of Analog Output is getting reduced at Higher frequencies from 5Vpk-pk to 0V  at 5K sampling frequency.   We are getting the 2.5V output at the RFBA pin without any Amplitude reduction at Higher frequcies.

 

   Now we have compared the Outputs at both the First stage 1st pin of AD8512 and  Second stage output 7th Pin of AD8512.

I herewith attached the Scope shot at higher frequency  for 1st stage and second stage output of AD8512 for your suggestion.

 

          In that what we have observed the following things,

 

1.At  1st pin of OP-AMP ,We are getting the constant output swing as    -2.5V  to 0V .There is no Amplitude decreasing at the Higher Sampling  Frequency

2..At 7th pin of OP-AMP ,We are getting the output swing with  amplitude is keep on decreasing at the Higher Sampling Frequency from  2.5vpk-pk to 100mVpk-pk at 5KHz Sampling frequency.

 

       We need support to solve this issue. Our required Analog Output samplin frequency is 40KHz.

 

 

Regards,

Sakthi.A.

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