BC547 v/s 2N2222 transistor

Discussion in 'General Electronics Chat' started by rahulrox1991, Apr 17, 2012.

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  1. rahulrox1991

    Thread Starter New Member

    Oct 31, 2011
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    I have a small circuit which controls the speed of a DC motor as per the ambient temperature. The circuit is working perfectly fine. I have across this circuit across a lot of forums and was just wondering if I could replace BC547 (Q1 in the circuit) with the commonly used 2N2222 npn transistor.

    I checked out the SPICE simulation of the circuit and power dissipation isn't an issue (which usually is under most circumstances for NOT using 2N2222). Any other reasons that you could suggest.

    Here is the circuit diagram - http://www.redcircuits.com/Page109.htm
    Thanks in advance :)
     
  2. chrisw1990

    Active Member

    Oct 22, 2011
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    have you looked at the datasheets?
     
  3. rahulrox1991

    Thread Starter New Member

    Oct 31, 2011
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    Yes I did... 2N2222 has a maximum permissable power dissipation of 250mW whereas BC547 can take 500mW. But the circuit is operating in 4-12mW range for Q1 transistor. So thats not a problem. Any other problem that you could think of?

    Any possibilty of temperature sensitivity? Since this circuit involves temperature control?
     
  4. chrisw1990

    Active Member

    Oct 22, 2011
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  5. chrisw1990

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    Oct 22, 2011
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    the only real place i can see where its lacking is the gain. everything else its surpassing the bc547.. :)
    id try it.. see how it works.. the gain of the 547 might be crucial to the circuit
     
  6. Ron H

    AAC Fanatic!

    Apr 14, 2005
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    BC547 will work just fine.
     
  7. rahulrox1991

    Thread Starter New Member

    Oct 31, 2011
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    will 2N222 work in its place? any possible issues?
     
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  8. Wendy

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    Mar 24, 2008
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    And the maximum dissipation for a metal cased 2N2222A is 600mw. You are looking at the plastic varieties.

    When it comes to thermal conduction, metal always beats plastic. Many plastic 2N2222A are labeled PN2222A.

    It is also possible to glue very small heat sinks on a transistor to increase its wattage, say a small piece of flat metal ¼" by 1/8 on the flat spot.
     
  9. Ron H

    AAC Fanatic!

    Apr 14, 2005
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    Oops! I had it backwards. Yes, 2N2222 will work fine.
     
  10. Ron H

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    The NPN in that circuit is coasting.
     
  11. Felo

    Member

    Feb 20, 2012
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    When I come across a replace for a switching transistor, I always choose over-kill so for this, 4401 would be my choice.
     
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