Quement Electronics


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tion diodes. Indeed, under certain conditions where germanium junction diodes are required, these can be ideal: e.g., lower sensitivity to transients, lower forward voltage drop. But remember that a silicon transistor becomes a silicon diode, and is just as sensitive to PIV overload.

A fact often overlooked is that the reverse-biased base-emitter junction of many silicon transistors makes an excellent zener diode in the G-12V range, depending on the transistor". Unfortunatelyt however, only good commercial transistors do well in this regard, and the dynamic resistance of surplus ones is often hopelessly high. Out of a dozen Fair child SE1002 transistors I tested, all had base-emitter zener voltages of the order of 6.5-6.7V at 1 mA, From a comparison of the resulting dynamic resistance with that of regular 6V zener diodes, I calculate that these are equivalent to a 300 mW American power rating, or 150 raW European or Australian power rating.

Thus, even half-damaged transistors can be put to good use, if the other half works. Perhaps in this day of affluence and low semiconductor prices, this may appear to be in the string-saving category, but my atti tude in matters of this kind is colored by years of supporting a potentially expensive electronics hobby on a student's salary, and partly by the fact that those 'inexpensive' semiconductors manage to become considerably dearer after Australian Customs and the local middlemen have had their bit. Even so, its great fun in VK7; why don't you come visit us sometime and see?


1. For example, see Silicon Diodes and Common Sense," CQ, Sept. 1965 and 4 Silicon Replacement for Tube Rectifiers," Q$Tt Jan. ]96f>; also "Zener Diodes", 73, October 1966.

2- Tins subject has been covered in some detail in a series of articles in The Australian Equipment Exchange Bulletin (P. O. Box 177, Sandy Bay, Tasmania, Australia) from -fuly 19^6 to July 1967.

3. See 73, November 1966,

4. "Protect Your VTVM'\ 73, August 1966, p. H2,

5. I strongly recommend the following articles to you: "Save That Transistor 7/f, July 1966.

MZener Diodes", 73, October 1966. "Zeners as Hi-Cap Variable Capacitors", Radio-Eleetroniex, September I966t

"Solid-State Tuning, Break-In, January 1966. "Varactors"; Break-In, May 19f?0. ("B*!" is the ZL equivalent of QSTf but ¬°ouch better because in part they show what more can be done with partial transistors, and because they continue this semiconductor discussion more fully on important and exciting propert ies.)

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