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AD737 scale factor and linerity

Question asked by DMN on Dec 9, 2013
Latest reply on Jan 14, 2014 by DMN

Dear all,

 

It seems that our measurement and the contents of the data sheet are not in agreement.

If you may notice, please let me know.

 

Q1.

  VR=200ohm is used for Fig.30 in the data sheet (page16)

  What kind of formula is the scale corresponding to this resistance?

  * in the case supply voltage +/-3.3V

 

Q2.

  If 22-ohms resistance is inserted between AD737-PIN4 and -Vs of schematics in Fig.30 in the data sheet,

  Linerity (Fig.14 in the data sheet page.9) will improve.

 

  Actual measurement when following Fig.14 :

    Input Voltage 100mV ==> Output difference error +0.3%

    Input Voltage 400mV ==> Output difference error -0.4%

    * Difference with error 0.7%

 

  When 22-ohms is inserted on Fig.14 :

    Input Voltage 100mV ==> Output difference error +0.4%

    Input Voltage 400mV ==> Output difference error 0.0%

    * Difference with error 0.4%

 

  When inserting 22-ohms in schematics, is there any problem?

  And, why does linerity improve?

 

Best Regards,

DMN

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