We're designing ADA4530-1 in our new product. We use CN0407 as our reference design. We have some questiones about the schemetic. Could you help us?
1. Does RC circuitry (RN1 (1-8, 2-7) and C47) work as a passive RC filter? Will it be better if we add an op amplifier, i.e. an active RC filter？
2. Why do you add RN1 (3-6, 4-5) and C9 to the input of AIN1? What do you concern about?
3. If we want to do system zero-scale and full-scale calibration, which channel should be active? Do you have reference code for system calibration?
Thanks in advance.
I didn't do this particular design, so hopefully that engineer can come up and provide some more details. But if you look at the block diagram of the CN0407 page it looks like these resistors are a combination of filtering and a matching network.
I would not replace with an active filter here, just because this is a femptoamp measurement system and I think any added noise, bias current, offset voltage, ect here is going to negatively impact your design.
I don't believe there is any reference code available, but you could check out the FTP recommended in the documentation to see what they offer in that software zip file. (ftp://ftp.analog.com/pub/cftl/CN0407/ )
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