Parallel BJTs

Discussion in 'The Projects Forum' started by Ardianwardhana, May 30, 2009.

  1. Ardianwardhana

    Thread Starter New Member

    Apr 2, 2009
    5
    0
    How to connect two or more power BJTs without ballast resistor?

    I done this by FETs. It was NTC, more current, more resistance, so it would self-regulate. But i heard that a BJT was PTC, so i thought if current is imbalance, it will catastrophically failed.
     
  2. mik3

    Senior Member

    Feb 4, 2008
    4,846
    63
    Yes, this is true nut BJTs have a NTC.

    If you parallel BJTs the hottest one will conduct more and more current and finally it will be destroyed.

    MOSFETs are good for paralleling due to their PTC.
     
  3. Wendy

    Moderator

    Mar 24, 2008
    20,766
    2,536
    Actually Hughs did it quite nicely with their gap welders, and the early models were germanium no less. The trick is to use low ohmage resistors to balance the load somewhat, and match the transistors if you have the know how.
     
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