Perforated Emitter technology

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

Graham

"John Popelish"

** 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

"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.

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

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.

--
"I\'m never wrong, once i thought i was, but was mistaken"
Real Programmers Do things like this.
http://webpages.charter.net/jamie_5

Safe operational area (SOA).

Graham

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.

Thanks.

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 trademarked.

Thanks for the assistance.

** 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

Will do. Thanks.

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

This patent:

mentions the "overlay" structure, as well as the "perforated" emitter structure.

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.