walid Posted January 31, 2007 Report Share Posted January 31, 2007 Hi all my friendsIn 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. Quote Link to comment Share on other sites More sharing options...
audioguru Posted February 1, 2007 Report Share Posted February 1, 2007 What is the differential i/p current, and how to ensure that it will not exceed 10mA? Quote Link to comment Share on other sites More sharing options...
walid Posted February 1, 2007 Author Report Share Posted February 1, 2007 hi guruIn 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 Quote Link to comment Share on other sites More sharing options...
audioguru Posted February 1, 2007 Report Share Posted February 1, 2007 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: Quote Link to comment Share on other sites More sharing options...
walid Posted February 1, 2007 Author Report Share Posted February 1, 2007 NOW I Understandthank you guru very much Quote Link to comment Share on other sites More sharing options...
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