what is (Emitter-Base Voltage)?

Discussion in 'General Electronics Chat' started by mostafa_gordy, Mar 14, 2013.

  1. mostafa_gordy

    Thread Starter Member

    Feb 28, 2012
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    what is VEBO (Emitter-Base Voltage) ?(in BJT)
    what is VBR EBO ( Emitter-Base breakdown Voltage)?
     
  2. JDT

    Well-Known Member

    Feb 12, 2009
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    85
    VBEO is the voltage between the base and the emitter when forward biased, with the collector disconnected.

    It will be specified at a certain base current. Normally around 0.65V for most silicon transistors.

    VBREBO is the reverse breakdown voltage of the base-emitter junction with the collector disconnected. It will be specified at a certain value of reverse current. Often in the region of 6V for small silicon transistors.
     
  3. mostafa_gordy

    Thread Starter Member

    Feb 28, 2012
    57
    0
    OK JDT....
    if more voltage of reverse breakdown voltage of the base-emitter junction is pass of base - emitter junction .... power Transistor is damaged.....? (bux15)

    BUX15 NPN 8A Vce =500V P=150w Hfe=15-60 (5 at 8A)
     
  4. ErnieM

    AAC Fanatic!

    Apr 24, 2011
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    Believe it or not, no, not at all. Think of it as similar to a zener diode: you normally operate those beyond breakdown but as long as the current is constrained it is fine.

    Way back when state of the art switching supplies used transistors it was not uncommon to whack the B-E junction past breakdown to pull current out and get them to turn off a bit faster.
     
  5. ramancini8

    Member

    Jul 18, 2012
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    It has since been shown that reverse breakdown of the B-E junction, even if current limited, causes long time beta degradation.
     
  6. Ron H

    AAC Fanatic!

    Apr 14, 2005
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    I have heard the same thing. A little Googling disclosed that Bob Widlar claimed that it will not damage high-current beta, such as that of a series-pass transistor in a regulator. I would like to see hard documentation on that before I believe it.
     
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