TO204 Transistor Package Basic Question

Discussion in 'The Projects Forum' started by jpborunda, Apr 22, 2014.

  1. jpborunda

    Thread Starter Member

    Apr 9, 2014
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    Hello everyone. Got this simple question about how to connect a TO-204 packaged Transistor. Looking at the datasheet for the BUV22, (NPN, power transistor) http://www.onsemi.com/pub_link/Collateral/BUV22-D.PDF, it comes in the TO-204 "package". This is the info from the datasheet: TO−204 (TO−3), CASE 197A−05, ISSUE K.
    However, Im confused about how to actually connect the device, since the datasheet doesnt say which lead is which, and It only has 2 leads.

    Looking at some other datasheets : http://www.onsemi.com/pub_link/Collateral/2N5038-D.PDF, I see that the CASE is actually the third terminal (Attachment) . So my question is, are the leads for the transistor always as specified in the second datasheet? And how do you properly connect the transistor (specially the CASE = Colector terminal), both in a PCB and a breadboard?

    I've never worked with these types of packages, so bare with me people :)
    Thanks !
     
  2. #12

    Expert

    Nov 30, 2010
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    I never bet they are all the same. It seems simple enough to use an ohm meter to find which pin (the base) is one junction away from the case.

    This case isn't intended for a breadboard or PCB. It's intended for a heat sink. You can drill holes for it, but you will never realize its full abilities unless you give it a heat sink.
     
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  3. THE_RB

    AAC Fanatic!

    Feb 11, 2008
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    The bottom left picture shows the pin numbers, 1 and 2 next to the pins. That picture is looking from the bottom of the case (looking at the pins).

    The case is connected to a PCB using a conductive screw and nut though at least one hole.

    That package case always has the B and E pins in the same locations, for every brand and every transistor variant. Case is always C.
     
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  4. jpborunda

    Thread Starter Member

    Apr 9, 2014
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    Thanks a lot for the answers! That clears up things for me.
    Now, if I may ask, does the BUV22 NEED a heat sink to work? I read somewere that the heat sink is only necesary when dealing with powers higher than the transistor's max.
    Thanks guys!
     
  5. #12

    Expert

    Nov 30, 2010
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    The transistor's, "max" means, "with a big heat sink".
    Without a heat sink, you are using Thermal resistance, junction to case, which is .7C/watt plus resistance case to ambient, which is not listed.
    If that was, say, 1.4 C/w, than your limit to get to 200 Centigrade is 83 watts.
    DO NOT BET ON THAT NUMBER.
    and do not run that transistor at 200 degrees C if you want it to last more than a few months.
     
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  6. jpborunda

    Thread Starter Member

    Apr 9, 2014
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    Ok, thanks a lot for the info! Usefull as always!!
     
  7. AnalogKid

    Distinguished Member

    Aug 1, 2013
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    What is the application? What are you using the transistor to do? Is it a linear amplifier, switching a load on anf off, etc.?

    Whatever it is doing, you can measure or calculate the power being dissipated by the device. That plus the environment it is running in can be used to calculate how hot it will get in free air, or with a small heatsink and fan, or however it is mounted.

    ak
     
  8. THE_RB

    AAC Fanatic!

    Feb 11, 2008
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    Like AnalogKid said we really need to see a schematic or at least more details about the voltages and currents and type of load.

    PCB mount heatsinks for TO-3 style packages usually look like these;

    [​IMG]

    [​IMG]

    [​IMG]
     
  9. DC_Kid

    Distinguished Member

    Feb 25, 2008
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    this npn is an obsolete product. replaced by BUV22G
    you have to dig on the distributor sites for links for the better docs
    http://www.onsemi.com/pub_link/Collateral/197A-05.PDF

    apparently there are different styles of the product case and each a different pinout.
     
    Last edited: Apr 24, 2014
  10. THE_RB

    AAC Fanatic!

    Feb 11, 2008
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    That would be incredibly rare.

    I've worked with TO-3 transistors for decades and NEVER came across one that was not B-E on the pins and C for the case! :eek:
     
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