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Hi all my friends
In the datasheets of  Lm308 attached below (at the end) I cut this part for discussion:


and here are the notes:


my questions:
1- What is the differential i/p current, and how to ensure that it will not exceed    10mA?
2- Please explain Note 1, I did not understand it?

Thank you very much.

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Hi Walid,
1) This very old opamp has input transistors with an extremely high current gain.
2) Therefore they have a very low breakdown voltage.
3) So the inputs have back-to-back protection diodes between them to conduct when the differential input voltage exceeds about 0.6V.
4) If the differential input voltage exceeds 1V then a very high current will flow and will burn out the protection diodes unless their current is limited to 10mA.

That is what National Semiconductor says and I just copied it.
Here is a pic that might explain it better:

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