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Transistor as a zener diode

  1. Jan 12, 2009 #1
    Can anyone explain about or point me to any articles about using transistors as zener diodes ?
    Why not just use zeners, and what connections (c-b short or e-b short) and their pros and cons ?
  2. jcsd
  3. Jan 12, 2009 #2
    When I was doing bipolar IC design, we reverse bias the EB junction as zener diode of 6.3V. We connect the B and C together to form the cathode and the emiter as anode. I don't know what voltage you can get with any transistor, but yes, it can be a zener diode. Whether it is optimized to work as a zener or not is a different story.

    That time the zener we get by reverse the EB diode has a +2.4mV/deg C, we always have to put a forward biased diode( CB as cathode and E as anode also) in series which have -2mV/deg C to cancel the drift.....approximately only, still not very good.

    If you do a discrete design, I would not use transistor as zener. Don't know even the long term stability and the current limit. Get a real zener.
    Last edited: Jan 12, 2009
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