How does a 2N3055 NPN transistor work?

[Bugman Jeff]

As the title states, how does a 2N3055 NPN transistor (http://www.radioshack.com/product/index.jsp?productId=2062614&tab=summary) work? I know hery little about electronics, so please keep that in mind. What does this transistor actually do? The RS website just says it's an "Amplifier and switch for regulator applications." It's got the three terminals, the Base, Emitter, and Collector. If you were going to wire one of these transistors into something, what would the wires from the three terminals connect to(power, ground, etc)? Thanks for the info.

[Ron W3FJW]

For a regulated power supply, the collector would be fed by the positive voltage from the rectifiers (or battery), the emitter would go to the power output terminal and the base would be driven by the regulator circuitry to set the output voltage.

[gigelus2k3]

Just like every other NPN (http://en.wikipedia.org/wiki/Bipolar_junction_transistor) BJT does. I'm not sure tho that the ancient 2N3055 (was playing with them some 25 years ago) is good for switching...

Do you have any particular application in mind or just picked one from the sidewalk and want to see what can you do with it?

Serban

[ebill3]

WOW! That 2N3055 has been a goodie and around for a long time. What do you want to accomplish?

Bill

[Ron van Sommeren]

http://en.wikipedia.org/wiki/Transistor
http://en.wikipedia.org/wiki/2n3055

Vriendelijke groeten ;) Ron

[hargard]

Hi have a look at this for real BASIC info

http://www.st-andrews.ac.uk/~www_pa/Scots_Guide/info/comp/active/BiPolar/page1.html

Its very basic and I dont mean that as a insult.
It has helped me to understand.

Regards Antony(UK)

[clicky]

WOW - this reminds me on my first steps in electronics... and using 2N3055 (pretty expensive transistors those days, at least for a teenager!) as photocells! :) LOL

[Ron W3FJW]

They're $1.43 at Newark Electronics. Used to be 5, 6, 7, dollars when they were new on the market 20 years ago. Have no idea what they'd presently cost in the UK.

[slipstick]

They're about £2.00 ($3.00) these days. Oh and they've been around A LOT longer than 20 years, introduced in the early/mid '60s IIRC....so more like 40+years).

So to be clear for Jeff, the 2N3055 is conventional NPN transistor which works like any other NPN transistor. Used as an amplifier the input goes to the base and the output is on the collector with a resistor to +ve. Used as a switch a larger on/off signal goes to the base and the thing you're trying to switch is generally connected between collector and +ve power.The emitter is usually connected to ground/0V. That's simplified and there are other possible configurations but they're the basics.

You can do the same with any NPN transistor, the only thing special about the 2N3055 is the amount of power it can handle....and there are plenty of more modern and more powerful transistors these days. Plus if it's switching not amplifying you want to do almost everyone now uses Power FETs (Field Effect Transistors) rather than conventional linear transistors because they're a lot more efficient.

Steve

[Bugman Jeff]

Thanks for the info. Below is a pic of the circuit I'm working on. Some of my symbols are wrong, but you should be able to see how it works. Bascially, this is what it does: Switch 1 is always on, powering A. flip switch 2, power is cut to A and simultaniously routed through the electronics ultimatly rapidly switching power on and off to B1 and B2. It does this because the electronics relay(left one) is switched on and off rapidly, powering and unpowering the transistors. What I would like to do is eliminate the left relay(fewer parts make things cheaper ;) ). Since transistors work as switches, I was trying to figure out how to use them directly to trigger the on-off cycles of B1 and B2. Now knowing how these transistors work, looks like it can't be done by simple rewiring :(

Is there a way to make this circuit work with off the shelf electronics(no chip burning) using a single relay? It needs to work on both 6V and 12V, and handle about 10 amps each for A, B1, and B2. Thanks.

[village_idiot]

10 amps... use a relay. Depending on the coil in the relay, you will not need such a large package to make the switch. The TO-220 case is designed to sink a lot of heat and I doubt the coils in the relay are going to require such a large transistor. Also you probably want to add some damping doides to the coil of the relays
http://books.google.com/books?id=EEcemABAU44C&pg=PA418&lpg=PA418&dq=relay+damping+diode&source=web&ots=yvoY_QDLel&sig=HSwebH6DYI3SfiOelqNrOdj0tB8&hl=en&sa=X&oi=book_result&resnum=15&ct=result

[topizz]

Just a word on this 2N3055 transistor. If my memory is good, they have a terrible low efficiency : for a 10A on the emitter, you will need to supply more than 1A for sure on the base (and I think the correct value was about 3A).
The saturated emitter-collector voltage was about 3A...ouch!

So clearly for full commutation, maybe another transistor will do the job better than this one, and probably a mosfet would have a much better efficiency.