LM308 maximum ratings

[walid]

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.

[audioguru]

What is the differential i/p current, and how to ensure that it will not exceed 10mA?

[walid]

hi guru

In fact, I did not understand anything from what u said. I know that the differential voltage is the difference between the two voltages applied to the two i/ps; the inverting and non-inverting.
can you explain it more?
thanks

[audioguru]

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:

[walid]

NOW I Understand
thank you guru very much