Looking for a compatible 2N4033 but in TO92

Discussion in 'General Electronics Chat' started by Mad Professor, Jun 5, 2010.

  1. Mad Professor

    Thread Starter Active Member

    Apr 15, 2009
    133
    1
    Good Day All.

    I am trying to find a compatible to the 2N4033 but in a TO92 package.

    And somewhere I can buy local, so in my case that will be Maplin or RS.

    Thanks for your time.

    Best Regards.
     
  2. Bychon

    Member

    Mar 12, 2010
    469
    41
    PNP, 80V, 1A, Hfe = 70@500ma
     
  3. Bychon

    Member

    Mar 12, 2010
    469
    41
    Try BC640 @ .27 lb.
     
  4. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    You may very well run into a power dissipation problem.

    The 2N4033's TO-39 package can handle up to 4 Watts (if properly heat-sinked), but the TO-92 package is limited to 625mW. It even has a minimum gain of 70 when Ic=500mA, and 25 when Ic=1A. That's going to be hard to find.

    You might look at a ZTX753; Farnell should have them in stock.
    Datasheet: http://www.diodes.com/datasheets/ZTX752.pdf
     
  5. Mad Professor

    Thread Starter Active Member

    Apr 15, 2009
    133
    1
    Thanks for your replys so far.

    I am trying to control a 5volt device from a micro-controllor, but the device in question pulls more current then the micro-controllor can safey handle.

    The sample design says to use a 1k resistor from the output pin of the micro-controllor, and then to the base of the 2N4033, 5volt supply on the emitter, and the load connected to the collector.

    Looking into it in more detail, I only need a max current of 500ma output.

    If this helps at all can you now advice a better suited item?

    Thanks for your time.

    Best Regards.
     
  6. Bychon

    Member

    Mar 12, 2010
    469
    41
    What? The transistors we named won't work?
     
  7. retched

    AAC Fanatic!

    Dec 5, 2009
    5,201
    312
    hello, it seems to me that the ZTX753 will do just fine.

    It can handle 2 amps continuous. Your request for 500ma is more than covered.
     
  8. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    I'm concerned that the gain for the ZTX753 is not high enough.

    Use a ZTX792A instead:
    http://www.diodes.com/datasheets/ZTX792A.pdf
    Distributors and stock are shown halfway down this page:
    http://www.diodes.com/products/catalog/detail.php?item-id=647

    Use a 270 Ohm resistor from the base to the uC's I/O pin. You want the Vce(sat) to be as low as possible without stressing your I/O pin. 270 Ohms will give you 15.9mA base current. This should give you a Vce of just over 0.1v (around 120mV according to the Vce(sat) plot on page 3 of the datasheet) which will give about 60mW power dissipation in the transistor, well within limits.
     
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