About AD620  Make vs. Buy Error Budget

Hi there,

I have a question about AD620's Table 4.

http://www.analog.com/static/imported-files/data_sheets/AD620.pdf

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.

Best regards,

Tarzan

AD620_Nonlinearity.pdf
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    •  Analog Employees 
    on Nov 16, 2014 7:18 PM over 6 years ago

    Hi Tarzan,

    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.

    Thanks!

    Kris

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  • 0
    •  Analog Employees 
    on Nov 16, 2014 7:18 PM over 6 years ago

    Hi Tarzan,

    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.

    Thanks!

    Kris

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