7805 voltage regulator in parallel

Discussion in 'The Projects Forum' started by BobW55, Mar 26, 2012.

  1. BobW55

    Thread Starter Active Member

    Jul 22, 2008
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    Can a 7805 be used in parallel to up the amperage?
    I need a 5 volt power supply that can deliver 1.5 amps continuous. I know the 7805 can provide a good 1 amp if well heat sinked but I need a bit more.

    Ideas?

    Bob
     
  2. wayneh

    Expert

    Sep 9, 2010
    12,103
    3,038
    The datasheet has example circuits for this.
     
  3. bretm

    Member

    Feb 6, 2012
    152
    24
    Any decent 7805 datasheet should include a schematic in the "typical usage" section that shows how to increase the current capacity through the addition of a power transistor and a resistor. For example, the datasheet for Fairchild KA78XX has Figure 12 "High Current Voltage Regulator" and Figure 13 "High Output Current with Short Circuit Protection".
     
  4. wayneh

    Expert

    Sep 9, 2010
    12,103
    3,038
    From TI, the same.
    [​IMG]

    [​IMG]
     
    #12 likes this.
  5. BobW55

    Thread Starter Active Member

    Jul 22, 2008
    43
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    Thanks for the replays.
    I have the same circuit on one of my data sheets.
    But the question still remains, can you run 2 of them in parallel?
     
  6. bountyhunter

    Well-Known Member

    Sep 7, 2009
    2,498
    507
    YES, if you do it right. If you have a bunch of them, select a pair that have close output voltage values. Then you have to put a series resistor from each output to the load such that there will be about a 0.2V drop across it at full current.
     
  7. MrChips

    Moderator

    Oct 2, 2009
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  8. BobW55

    Thread Starter Active Member

    Jul 22, 2008
    43
    0
    Being a cheap person, I found 10 of the 7805's in my junk drawer.
    Have to order some other parts anyway just add a regulator to my list.
    Just thought I could save a buck.
    I may have a 6133 laying around somewhere, but I still need some caps, relays, couple switching transistors, Glcd, Pic, and a quadrature encoder.
     
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