[sdiy] starter components -- one of everything?

[harrybissell]

I just predicted that you would ask another thousand questions. I'm
psycho, you know...  :^)

Why some parts can replace others...

Some circuits use only a basic property of the component.  An NPN
transistor,
(common emitter) with a positive voltage on the base, will cause a
collector current to flow. If you wanted to light an LED in series with
the collector (takes about 10mA)
and you provide maybe 1mA current to the base, just about any transistor
on GOD's
green earth will do the job.

If you were counting on a large amount of gain... maybe you only have 1uA
to drive that base with... you will need a specially (carefully) chosen
device.  Likewise if you
need 1A of collector current... etc.

Usually a s-diy designer will tell you if you can substitute parts. In a
commercial
design... you will need to study it to figure out the designer's intent.
Is he (she)
relying on some special characteristic of the device... or just the basic
operation ?

There are two classes of designer. There is no way to tell them apart.
They are either

1) Total Idiots  ~or~  (more likely)
2) So clever that you cannot understand just how elegant their design is.

Usually I suspect the former, and after a lot of pain (and study) I find
out they are the
latter.  Especially (imho) Bob Moog, who makes a single component do about
four
things at once. Mess with ONE of them and you upset the other three :^P

There are some good online sites but I can't think of them right now.
Somebody
help me out !!!

H^) harry

Johannes Öberg wrote:

> I realized that what I'm looking for is probably a book on the
> subject... I found
> http://home1.gte.net/res0658s/electronics/parts_subs.html  but I would
> like to learn _why_ some parts can replace each other while others
> can't. Maybe I'm looking for an (on-line, preferably) electronics book
> just above the basic "what's a diode?" level :-) Anybody have anything
> to recommend?
>
> /Johannes