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AD8422 Test Result Check

Question asked by Jiwon.Lee on Aug 26, 2016
Latest reply on Sep 18, 2016 by Jiwon.Lee

Hi,

 

I'm trying to find out the reason of difference result with voltage divider at the VIN+/VIN- inputs and without it.

Can you please help me to find out the reason ?

 

Test 1. : Diamond Plot

                  Input : Vin+ = +3V DC, Vin- = GND

                  Output = 3V

 

Test 2. : EVB(EVAL-INAMP-82RMZ with AD8422) Test without voltage divider, RG = Open

                  Input : Vin+ = +3V DC(From Power Supply), Vin- = GND

                  Output = 3V

 

Test 3. Real Circuit Test with voltage Divider(R1=1M, R2=330K, R4=330K, RG = Open)

             Input(Vin =+12V, Pin4 of AD8422 =12V*330K/1330K) = 2.977V

             Output = 0.2V  ==> Expected to get 2.977V, but 0.2V

 

Question : Test 1 and 2 shows expected same results, but Test 3 is different.

                 Does voltage divider affect the different result ? Why the output is not 2.977V at Test 3 ?

 

Thanks.

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