uln 2803

Discussion in 'General Electronics Chat' started by FroceMaster, Apr 13, 2015.

  1. FroceMaster

    Thread Starter Member

    Jan 28, 2012
    400
    4
    Quick ? about this uln2803
    can i just use it as a replcement for normal transistor.
    Like in the schem..
    most i think is the pin 10, is that commond ground for all transistors ?
     
  2. MikeML

    AAC Fanatic!

    Oct 2, 2009
    5,450
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    As long as you realize that the innards are more complicated than a transistor:

    uln.gif

    Pin 9 is E (gnd). Pin10 is COM (used as a snubber for inductive loads)
     
  3. MaxHeadRoom

    Expert

    Jul 18, 2013
    10,515
    2,369
    Bi-polar Darlington configuration, fairly high impedance input.
    Max.
     
  4. ian field

    Distinguished Member

    Oct 27, 2012
    4,413
    782
    Don't forget those devilish little details - you need double the Vbe to turn them on, and you can't saturate a Darlington.
     
  5. eetech00

    Active Member

    Jun 8, 2013
    649
    112
    It depends on how you intend to use it. Post description and/or schematic please?

    eT
     
  6. ScottWang

    Moderator

    Aug 23, 2012
    4,853
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    When you using bjt as a driver then maybe you can using uln2803 to replace it.

    The uln2803 provided the collector-current rating of each Darlington pair is 500 mA, and also the total current is the same, in most situations that you just using the current less then I = 500 mA * (1/3) = 166.67mA, whatever each or total, the better way is to using the total current as I = 500 mA * (1/5) = 100 mA for the heat issue, what is the best balance point for the current and heat, when the IC can be touch with fingers and it just has a little warm, but not hot.
     
  7. FroceMaster

    Thread Starter Member

    Jan 28, 2012
    400
    4
    foforgot the Picture. just think of 5 volt as TTL output
     
  8. MikeML

    AAC Fanatic!

    Oct 2, 2009
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    Do not ground pin 10. Either tie it to +5V, or let it float.
     
  9. ScottWang

    Moderator

    Aug 23, 2012
    4,853
    767
    You can see the practical application as below, uln2003 is the same as uln2803 just less one driver, you can let the inputs floating or connected to ground, the common pin of diode can be float or connect to +5V, when the load is relay or coil must be connected to +5V.


    [​IMG]
     
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