--- In
motm@yahoogroups.com, Tentochi <tentochi2003@y...> wrote:
> I know some of this has been mentioned here before, but I forget
all of the
> details and I can't find it in the archives.
More complete info can be had on the web from the datasheets for each
of these devices.
>
> Can someone please explain the differences between the BC549 and
BC550 and also
> between the BC559 and BC560?
There is very little difference aside from the average gains and
noise from a given number of tested devices. The difference between
the 549/550 and 559/560 is polarity- the former is NPN and the latter
is PNP. Transistors have quite wide tolerances. It is not uncommon
to find great variations in noise or current gain (hFe)when testing
even a small number of devices. In most circuits, this won't make
any difference. In fact, as long as the transistor has the correct
polarity, you can usually substitute freely with only minor resistor
value changes to make sure the device pulls enough current. You may
get more or less noise, but those differences would occur within a
single transistor part number!
>
> Second, what are the differences between the A, B and C types?
What if an A, B
> or C is NOT given after the part number?
See above. These letter suffixs usually denote "improvement" in the
average specs of a specific number of tested devices. In some cases
these specs can be radically different (BC108C's come to mind, with
average hFe of 500!)
>
> Are there any practical differences between these transistors when
they come
> from different manufacturers? In particular, Vishay and Fairchild?
Not anymore! You can bet that your transistor was made by little
girls in some Asian country while being physically and mentally
abused, regardless of the name on the label. There shouldn't be any
variation in the average specs (see above) but it would be impossible
for the average user to tell, much less care.
>
> Thanks!
> Shemp
It's my job, sir and your'e welcome. For a really good learning
experience, build a small, single transistor, common emitter
amplifier circuit on your protoboard. Then drive it with a bit of
white noise or a square wave and watch the output on a 'scope. Heck,
you could even listen to the difference through an amp and speaker.
Leave all the components the same but change transistors. Even
within the same part numbers/suffixs/manufacturers, you'll be able to
discern the differences.
Chub
ps- remember the word "transistor" is a contraction of two words -
Transistional Resistor. Dropping that bit of tid in conversation at
cocktail parties will guarantee that you'll never be invited back!
Perfect for avoiding dull events while you work on your music!
>
>
>
>
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