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electronics

Started by Uthman Jan 12, 2005 at 4:15 PM 2 replies 450+ views

Original Post

Jan 12, 2005 at 4:15 PM

i don't know why, but im having a hell of a hard time understanding transistors. i've read over fifteen googled 'how transistor works' articles, but its just not clicking. i perfectly understand diodes, but why transistors work, how come there are dual depletion areas, how come there isn't current feedback, etc. Im coming from a background where i understand semiconductors having taken materials science classes and basic basic circuits from physics. I know this isn't a clear question, but If I knew exactly what it was I didn't know I'd know it ':/

etothex

Jan 12, 2005 at 5:11 PM

Unipolar or bipolar? I assume you've read wikipedia already?

Uthman

Jan 12, 2005 at 5:26 PM

bipolar, and yes.

i checked another tutorial in the mean time titled 'how transistors work, an alternate viewpoint' which helped alittle, but i am *still confused on why when the depletion between the base and the collector is larger than that of the base and emiter, more charge is pumped in that direction

Talib

Jan 13, 2005 at 8:02 AM

A bipolar junction transistor(BJT) has three layers of differently charged materials. IE NPN or PNP.

Transistor as switch (easy explanation) NPN:

circuit 1: Connect a supply (lets say 5V), positive to the first N (or collector) and negative to the second N (emittor). Because both are connected to N it is said that loop is reversed biased (IE no current will flow)

circuit 2: As soon as another supply is connected across the P (base) and N (emittor) and the voltage across it increase to above +-0.65V the transistor will switch on and current from the first circuit can now flow.

Now transistors can also bu used in different configurations to do different things:
Amplifier (Common base, common collector, common emitor)
Constant current source
etc.

For more info you need to look at first year electronics.

If you need more explanations I can prolly draw you some pics and stuff.
Lemme know!

Talib

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