AD8228 Gain strapping


I built two amplifiers with gain set to X100

The intended use it to increase the accuracy of some automated test equipment.

It will take 4-wire resistance measurements

I am trying to get a gain of 100, but I am seeing a gain of ~0.7 for both In-AMPs.

This is wired up correctly?

What did I do wrong?



  • 0
    •  Analog Employees 
    on Aug 19, 2020 1:15 AM 6 months ago

    Hi David,

    Thank you for using AD8228 in your intended application.

    Regarding your inquiry, May I clarify the voltage levels on your AD8228 pins? like your VSS+ and the voltage at Vin+.

    I also noticed that you're using the AD8228 in single supply scheme and having the reference pin on GND (please correct me if I'm wrong, I'm thinking that the symbol on the CH6, CH2, CH3, etc. are ground.)
    If this is the case, you're probably operating outside the input common-mode voltage of the AD8228. You can check this online Diamond Plot Tool to play around with the input configuration of your AD8228 to see what will work on your setup. Also you can watch this video to see how to work with the Diamond Plot Tool.

    Let me know if you have more concerns David.

    Best Regards,