Page 180 - Troubleshooting Analog Circuits

Letters to Bob I67

obstinately refuses to do your bidding is almost certainly a consequence of your
imperfect understanding of its menus and possibly also of your failure to read the
manual all the way through-which you’ll do the next time you have a spare week.
Keep up the good work.

Reginald W. Neale
Connoisseur of Solder Globs
Rochester, NY

Dear Mr. Neale.

Thanks for the good words. But, hey, water at 17 OF isn’t such a terrible idea if you
allow for a little antifreeze. The real problem I foresee is that you can easily get your
17 OF water in the winter, when you don’t need it. When you really would like to get
some is in the summer, and then it’s pretty expensive to chill it down that cold.
Maybe all you need is the plumbing equivalent of the solar-powered night-light with
the 12,000-mile extension cord.

RAP

Dear Bob:

I’m really confused by your apology on page 34 of the November 23, 1989, issue
of EDN. I understand about diode-connected transistors; we use them often.
However, we connect the base to the emitter and thereby use the base-collector junc-
tion. The breakdown voltage of such a connection is typically about the same as the
transistor’s maximum V,, rating. If we use your method, the breakdown rating will
be only 5 to 7 V typ, according to data sheets. I usually want more.

John Paul Hoffman
Caterpillar Inc.
Peoria, IL

Dear Mr. Hoffman:
You’re right, the collector-base junction can handle more voltage than the base-
emitter junction, but it’s also slower.

RAP

Dear Bob:

A few years ago, when I first moved into a new house and hooked up my stereo,
the left channel decided to fry the output transistors. The power amp had heavy feed-