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Concerning the need for an anti-swamp resistor(s)

  1. May 20, 2015 #1
    Why are .1R/5W resistors, known as "anti-swamp" resistors, required in a multi-parallel legged current booster schematic using an LM317 variable voltage regulator schematic when no resistor is shown on a single parallel legged current booster schematic using the same LM317? variable voltage regulator? This is not to be used in a audio amplifier configuration.
     
  2. jcsd
  3. May 20, 2015 #2

    berkeman

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    Staff: Mentor

    Link to schematic...? :smile:
     
  4. May 20, 2015 #3
    Hello Berkeman,
    I am do not see any schematic (reference your reply) to link to. Can you please send me directions on where and how to do so.
    Thanks,
    Scott McKie
     
  5. May 20, 2015 #4

    berkeman

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    Staff: Mentor

    Where did you see the circuit? Can you scan it and upload it? Or worst case, take a picture of it with your cellphone and upload the picture? I'm not familiar with the term "swamp resistor", so I'm not sure what to do a Google Images search for...
     
  6. May 22, 2015 #5

    Baluncore

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    Science Advisor

    The resistors balance the current from the multiple supplies. If one supply provides more current then it may get hotter and the temperature coefficient may increase the current further, leading to failure. It will be swamped.

    The VBE of power BJTs has a negative temperature coefficient. A series 0R1 is sufficient to keep the currents and temperatures similar.
     
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