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Perforated Emitter technology

Discussion in 'Electronic Basics' started by John Popelish, Oct 6, 2007.

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  1. I recently came across the data sheet for the MJL21193/4
    series of transistors for linear amplifier applications,
    and see that they describe them as being made with
    "Perforated Emitter technology". But I am having trouble
    finding out exactly what that means.

    What is it, and where can I find the details? Thanks.
  2. Eeyore

    Eeyore Guest

    It's a multi-emitter technology AIUI, designed to reduce secondary breakdown

  3. Phil Allison

    Phil Allison Guest

    ** The very first hit on Google is:

    Which not only describes the technique and it purpose ( enhanced gain
    linearity) - but also has close up pics of the MJL21193 chip itself -
    see figs 4.1, 2, 3.

    A tiny bit more digging reveals that Toshiba originated the technique and
    passed it on to ON.

    ........ Phil
  4. Phil Allison

    Phil Allison Guest

    "John Popelish"

    ** Some more digging produced a couple of app notes that mention the term "
    perforated emitter " and a nice pic of a device chip showing the actual "
    perforations " !!!

    Various benefits are claimed for having them, including very low Vce sat. VCESAT WHITE PAPER.DOC

    Seems that it is a " state of the art " design technique for BJTs, so
    makers are still a bit coy about giving away secrets.

    ....... Phil
  5. Jamie

    Jamie Guest

    We've use those before. I thought i've seen that number some where.
    now to think about it. We made a DC servo amp with them. It could
    of been made with others of course.

    I think the reason we tried those were due to the gain curve and
    voltage handling.
  6. Eeyore

    Eeyore Guest

    Safe operational area (SOA).

  7. Which is the first thing I found and found to be pretty brief.
    The test directly above those pictures is "This is also a
    good example of the "interdigitised finger" type of emitter
    and base construction referred to above." I don't think
    these are pictures of MJL21193/4 type devices. Those are
    the pictures I have been searching for.
  8. Lots of bragging, not many process or mask details.
    Finally, a picture. Thanks. It looks like there is a
    second layer of metalization over the die for the base with
    feedthroughs to the base fingers, to keep the base finger
    drop to a minimum.
    That might well explain the lack of cross sections, doping
    profiles and other details in public view. I am wondering
    if Zetex uses this technique for their low saturation, high
    gain, high current transistors. They don't seem to be
    bragging about it, but perhaps "Perforated Emitter" is

    Thanks for the assistance.
  9. Phil Allison

    Phil Allison Guest

    "John Popelish"

    ** They most definitely ARE pics of a MJL21193/43 chip.

    Rod Elliot is simply mistaken - I will inform him shortly.

    See ABSE now for pics of one from my collection.

    ....... Phil
  10. Will do. Thanks.
  11. The Phantom

    The Phantom Guest

    Remember the RCA "overlay" RF transistors? The 2N3866 is one such.

    This patent:

    mentions the "overlay" structure, as well as the "perforated" emitter
  12. I remember seeing the phrase "overlay RF transistor" but
    never knew exactly what it referred to.

    Here is an interesting article that evaluates many different
    semiconductor structures as high conductivity per area, high
    voltage, fast switches and proposes an advancement to the
    best case (surprise, its the bipolar junction transistor).
    Figure 13 shows the proposed enhancement, that looks like
    the ultimate in perforated emitter technology, but I don't
    know if anyone makes transistors this way, yet.
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