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AD7124-4 Pseudodifferential

Good day,

I use from a Pseudodifferential opamp architecture at the inputs of ADC. It means that the inputs comming from the Sensor will be amplifier at gain=50 and shifted by 1.5V and finally goes to AIN_P.

On the other hand, 1.5V also is connected to AIN_N.

My Question: is it possible to remove the final amplifier stage and instead, use from the internal PGA of AD7124?

I already did this for differential configuration but for the Pseudodifferential I have no idea how to shift the level by 1.5V for internal PGA.

Thank you for your time and considerations.

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  • Hi, 

    Apologies. I missed this one. 

    If the bridge is also supplied using single supply. Then I suspect that the common mode is positive? So I am not sure why do you need to shift it by 1.5V? If the output voltage at Senor P and Sensor N is positive and is within the ADC input voltage range then you do not need an external amplifier. 

    And one more thing, I would also suggest to configure your system in a ratiometric configuration wherein the reference and excitation voltage used are the same. Please see this reference circuit you can use this as a reference, It uses different product but the same scheme/approach can be use. CN0102 Circuit Note | Analog Devices though AD7124 can only operate up to 3.6V so 3.3V excitation can be use. 

    Thanks,

    Jellenie

  • Hi

    Thank you so much for the this informative answer.


    With the best regards