Offset: Temperature Coefficient total in PGA using AD797 and ADG412

Hi all:

Do anyone know how the calculation of the total temperature coefficient show in "Analog Device" literature of PGA, using AD797 and ADG412, increases from 0.6uV/ºC to 1.6uV/ºC? There is a 1uV/ºC part, not belonging to the AD797B, I am not able to work out. Any help is appreciated


Thank you

  • 0
    •  Analog Employees 
    on Sep 3, 2014 6:55 AM

    Hi Roberto,

    Thanks for your interest in using ADI products. According to the MT-072, offset temperature drift is affected by the change in bias current and RON. Therefore we need the following data to compute for this additional 1 uV/ºC offset temp drift.

    From AD797 datasheet:

    The mini tutorial is using the B-grade for AD797. From the graph, we can interpret it as:

    For 25 ºC, the Ibias is equal to 0.9 uA.

    For Tmax (85 ºC), the Ibias is equal to 2 uA

    From ADG412 datasheet:

    For 25 ºC, Ron = 35 ohms

    For 85 ºC, Ron = 45 ohms

    Given this, we can now calculate the additional drift as shown below:

    :Let me know if you need anything else.

    Best regards,

    Emman

  • 0
    •  Analog Employees 
    on Sep 18, 2014 4:24 AM

    Hi Roberto,

    Glad it helped. We also encouraging our customer to mark our answers either helpful or correct answer.  This will help others who have the same question to quickly see if the replies is right and useful.

    Thanks and best regards,

    Emman