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AD7124-8 Input impedance

Question asked by Fokstrot on Sep 13, 2016
Latest reply on Sep 19, 2016 by jcolao



Attached is a shema of the input stage ADC

V1,R1-R5 –imitation diode microwave sensor

V2, R6-R8 – bias voltage for unipolar power

U(V1) – 1.4 В. U (R3)~ 100 uV.

For Gain =1     U (ADC)~ 47 uV

For Gain=4        U (ADC)~ 41 uV

For Gain=16     U (ADC ~ 23 uV

For Gain 128     U (ADC)~ 23 uV

After each change of gain is calibrated Internal Full scale and Internal system zero

Why after changing the amplification of the measured signal is distorted?

What ADC input resistance and it depends on the gain?