Transistor dissipation

Discussion in 'Homework Help' started by zero_crack87, Sep 3, 2008.

  1. zero_crack87

    Thread Starter New Member

    Sep 3, 2008
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    why the specified maximum power dissipation of a power transistor at an ambient temperature of 25 celcius is much less than maximum power dissipation at a case temperature of 25 celcius?
     
  2. beenthere

    Retired Moderator

    Apr 20, 2004
    15,815
    282
    Please refrain from "hijacking" existing threads with tangent or off-topic questions. You can create new threads for new questions using the "New Thread" button on the upper left of the page.

    That's not how it works. The dissipation is rated at 25c and gets derated by some fraction of a watt for each rise in case temp above 25c.
     
  3. Audioguru

    New Member

    Dec 20, 2007
    9,411
    896
    How are you going to keep the case at 25 degrees C when the transistor is hot?
    The case will also get hot then the chip will be too hot. So you must reduce the power.
     
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