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LM311 queries..

Discussion in 'Electronic Basics' started by Ankur, Jan 30, 2004.

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  1. Ankur

    Ankur Guest

    hi,
    Cant experiment this out at present so am asking u ppl the following
    :

    If i leave one of the input pins OPEN and apply an input voltage to
    the other ... wht will b the output ?
    Suppose , i leave pin2 open then wht will b the output when i apply a
    +5V at pin3 (and a -5V at pin3) ??
     
  2. Look at the internal schematic on page 18 of the data sheet:
    http://cache.national.com/ds/LM/LM111.pdf

    The inputs are through PNP transistors that need a pull down bias to
    turn them on. So an open input acts as a positive voltage at the most
    positive end of the common mode voltage range. On page 4, the input
    range is listed as high as 13.8 volts with the +- 15 volt supplies
    indicated in note 15. So an open input (either one) looks like a
    voltage about 1.2 volts below the positive rail.
     
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