OPA928: OPA928

Bo Zhang

Prodigy 10 points

Part Number: 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！

5 天前

0 Links 3 天前

TI__Expert 5260 points

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.ti.com/lit/ug/sbou282a/sbou282a.pdf?ts=1721353967149&ref_url=https%253A%252F%252Fwww.ti.com%252Fproduct%252FOPA928

0 Bo Zhang 3 天前回复 Links

Prodigy 10 points

Thank you very much for your reply.

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

0 Links 3 天前回复 Bo Zhang

TI__Expert 5260 points

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.

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OPA928: OPA928