I have a question about AD620's Table 4.
About the Homebrew circut caluculation, where does Gain Nonliniarity spec"40ppm" come from?
I checked OP07D datasheet, but it does not look like the datasheet mention this spec.
Unfortunately, the datasheet for the AD620 was written over 20 years ago so we do not have a direct resource to provide you with this information. Most likely, it came from the characterization…
Unfortunately, the datasheet for the AD620 was written over 20 years ago so we do not have a direct resource to provide you with this information. Most likely, it came from the characterization data of the OP07D. A resource you can use for calculating nonlinearity for op amps is MT-044. Take note, however, that because 3 op amps are used for the "home brew" in amp, the linearity cannot be added directly. The errors from the op amps may interact differently - they may cancel, add together - the results would most likely differ. It is possible that the nonlinearity error on the AD620 datasheet may have been calculated using an equation such as the one in MT-044 with the assumption that the errors were equal. However, it is also likely that a direct measurement was taken from the overall discrete 3 op amp in-amp.
I apologize that I cannot give you a more concrete answer given the age of the datasheet. Out of curiosity though, are you considering making a discrete 3 op amp in amp? What specification do you require from your in amp? We have a lot of in amps in our portfolio and I believe we could find one that suits your requirements. Let me know what you need for your application and I can try to find one for you.