Re: Electronic newbie question regarding components


"George C." <harley.davidson@xxxxxxxxxxxx> wrote in message
news:44783e52.2416327@xxxxxxxxxxxxxxxxxxxxxxxxxx
Do I understand correctly that even 2 identical components (same brand
and part number) can perform not quite as well as the other?
In such a case, what's the way to get the 'ideal' component? Just keep
buying them and testing them to see which one gives the desired
values?

This is true. Most of the time, though, the differences are so slight as to
not matter.

I'm guessing that when we're talking about mass-produced components, such as
diodes, transistors, resistors, etc., the larger the number of your
production run, the more identical the parts will be toward one another.
But if you're making only small quantities of something, chances are the
differences will be more noticeable.

I sometimes run into power-control circuits in which output transistors have
to be "matched"; that is, you don't want one transistor carrying more of the
load than the other. I personally don't like this and consider it poor
circuit design. It shouldn't have to be that critical. What's worse,
having to order a large batch of replacement power transistors and being
able to match up only a few out of a couple of dozen runs into money. It's
especially aggravating when you see different logos on different
transistors; each manufacturer has its own special way of making parts, and
you can bet that they won't match exactly with the same part made by
somebody else.

Fortunately, there are not that many instances in which "matching" is really
critical. RF circuits can be, though, particularly when you're dealing with
a balanced modulator; if the diodes aren't matched up just right, you may or
may not be able to get it to balance.

From my experience, the best way to get "matching" parts is to order a large
batch from the same manufacturer, hopefully from the same production run.


.

Relevant Pages

  • Re: Trying to understand how to design circuits
    ... signals for the next stages to build on. ... Each pair of transistors facing each ... In electronics, the first ... and all other sorts of stiff, constant-voltage circuits. ...
    (sci.electronics.design)
  • Re: Transistors
    ... your spice model isn't set up to handle self-heating, ... with these transistors (that would be the real test, ... opamp circuits are a past my interest. ... for the low side of the class-AB bias voltage. ...
    (sci.electronics.design)
  • Re: get rich thru doing science
    ... op-amps and transistors, plus a few logic gates, but nothing more ... Thevenin + Norton equivalent circuits ... This was a semester length course offered by the physics department. ...
    (sci.research.careers)
  • Re: Throughput per transistor, the means to performance per watt?
    ... thread performance (HW engineers do the hard work, ... this trend has changed: the circuits won't become ... Instead multiple cores will move some hard work to SW engineers;-) ... Why do the 125 million transistors in a Prescott threaten to melt the ...
    (comp.arch)
  • Re: Marriage is under fire!!
    ... >> bipolar transistors, ... I posted an analogy to show why this might be incorrect (the ... the person building the circuits would see a clear agreement with the ... html mail or attachments will go in the spam bin unless notified with or in the subject line. ...
    (sci.electronics.basics)