Couple Of Questions Relating To Components

Hi all, I have a couple questions. Recently I got back into analog circuits and would like to better understand components and their use.

My first question is what is the practical application of a capacitor? I know that they charge/store energy, but I don't understand their practical use.

Secondly, transistors. I don't really know what they do or their practical use.

Oh and LED's, I've only played with them a little bit. Are all LED's diodes? how do I tell how much voltage I can feed into one before I destroy it without actually destroying it?

This post has been edited by Nituvious on May 06, 2012 04:02 am

Hrm, depends what you mean by "practical applications". A look through wikipedia can probably get you started rather than us reinventing the wheel for you, but...

One of the things capacitors do is store energy, yes. This is useful to smooth irregular current (say, when turning AC into DC). Or, they can be used to store energy when it's needed for surges, like bass notes in a song, rather than having an amp that can provide that peak amount continuously. It's also useful, in small sizes, when you can predictably say how quick it will charge or discharge, for timing circuits. They can be used to split or block different frequencies that are on the same line because they affect different frequencies in different predictable ways. But it does more than just store energy, it affects the phase of the electricity that passes through it in an opposite way that a coil does.

Transistors, again many applications and many different types. The two main groups of uses are: as a switch and as an amplifier. They allow you to control a big amount of power with a small amount.

LEDs. Yes all LEDs are diodes. Hence the acronym "Light Emitting Diode." You can tell how much voltage generally by reading the specs. But, voltage regulation is a bad idea for them, instead, plan for current regulation.

These generally aren't the kinds of questions you want to be asking people to answer personally, as any basic reading up on them from any source will tell you as much as you want to know. No better us than a fixed source that is already written.

a major practical application of capacitors is to block DC while allowing the flow of AC .

finding a good source of information about components these days is both easer and more difficult at the same time ...
it used to be that libraries carried a few books that were good ... even the smaller ones in smaller towns , not so anymore .

with the advent of the internet , separating the wheat from the chaff (or the flyspecs from the pepper) can be frustrating and time consuming .

asking basic questions about sundry components is ok ...
a deeper understanding requires some study and practical application situation .
dig out the breadboard and fire up the soldering pencil .

as for leds ...
they are devices with a low forward resistance ... like regular diodes and neon lamps .
you can determine the operating voltage (Vfwd) by hooking one up as one would a shunt regulator zener diode (with a current limiting resistor) and measure the voltage while observing the current with a mA meter (do not go over the max current recommended) .
many years ago some manufacturers used leds as voltage references/regulators .
i was surprised the first time i seen such a thing ...
there was the regulator circuit with a regular looking glass diode that glowed red !

You might check our Pinned: Links! page. There are several tutorials listed there.

Practical uses include energy storage for immediate release, blocking of DC while passing AC, & also their properties interact with those of resistors & inductors to form filters, which are circuits that respond differently to different frequencies. These properties are also useful in timing applications, which basically rely on the slow charging or discharging of a capacitor through a resistance.

Transistors are basically devices that control the flow of electricity. They control large amounts of power with very small amounts. All types basically do the same thing.


All LEDs are diodes, & each color has it's own characteristic operating voltage, called a 'forward voltage drop'. LEDs also have very narrow operating voltage ranges, which makes it much easier to use current limiting for many applications, as this makes the applied voltage much less critical. The forward voltage drop information can be obtained online, or from the LED manufactirer's datasheet.

All electronic components have datasheets, BTW, & these are the primary source of reference info for any given component. Most are available from an online search.
Here is a custom search engine for component datasheets. It excludes many of the spam oriented marketing sites.
http://www.google.com/cse/home?cx=01024407...6%3Avwhgg2nax4e

Thanks for the replies, guys.
My first course of action was to google my questions but I don't exactly have the ability to read:


Thanks for answering the questions, guys. I will try to keep my questions to a bare minimum and more deserving of this board.

This post has been edited by Nituvious on May 07, 2012 09:27 pm

Yeah, I know the feeling.

Some people, that's the "simple" way of explaining something, they look at it and go "See? Isn't that easy? It all makes sense."

And I, same as you, gloss over it and go looking elsewhere. Maybe not because I *can't* figure it out, but because of how tedious and frustrating it would be to square peg a round hole.

But, there are lots of basic layman's electronics explanations out there. If it gets too hairy, skip it and read a different one.