Parallel BJTs

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

  1. Ardianwardhana

    Thread Starter New Member

    Apr 2, 2009
    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
    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


    Mar 24, 2008
    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.