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
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.
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Thank you so much