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Trying to understand AD8138 circuit from legacy design

Category: Hardware
Product Number: AD8138

I am working with a legacy design using an AD8138 to drive an ADS5281. I'm trying to understand the following circuit:

The feedback resistors are symmetric at 1k2, but why are R65 and R63 split as they are, and what is the purpose of the R74/R68/R66 network? Why are the input resistors not simply symmetric?

C1ROH is an analog input from a back-plane connector. The input range is supposedly +/- 3V. The ADS5281 has 2 Vpp input range.

Top Replies

    •  Analog Employees 
    •  Super User 
    Feb 13, 2024 in reply to tgbe +1 suggested

    Hi  ,

    Good day. The resistors at the input should be symmetrical to avoid mismatch errors. You might want to use ADI's DiffAmpCalc to redesign your circuit. Here's the link for download: https…