OPA928: OPA928

I want to use OPA928 measure the current at the level of 10 fA,and the range of  10 fA to 100 nA. I have some questions:

1) How to select the best feedback RES.  Is  100 MΩ OK?

2) How to choose the material for PCB? Is FR4 four-layers PCB suitable?

Waiting for your reply, thank you very much！

Links：

1) How to select the best feedback RES.  Is 100 MΩ OK?

A 100 M Ω resistor may be suitable for your application, but it depends on the input bias current and noise characteristics of OPA928. Please take a try according to your application.

2) How to choose the material for PCB? Is FR4 four-layers PCB suitable?

FR4 four layer PCB is a reasonable choice, but please ensure that the PCB design meets the requirements for precise measurement of low current.

TI provided a EVM below, you can tale a look

https://www.ti2k.com/wp-content/uploads/ti2k/DeyiSupport_放大器_sbou282a.pdf

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Bo Zhang：

Thank you very much for your reply.

I have reviewed the document of EVM. But there is no information about the material of PCB.

,

Links：

Welcome, Bo.

Actually,FR4 can work for that.

If this answered your question, I'd appreciate it if you could click the Green button to let us know.