Electronics > Beginners

transistors

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queennikki1972:
Nothing I build with the small black silicone based transistors like the BC547 seem to work. I need a book or something to understand them better. I google the direction of the pin out for emitter base and collector, but none of them seem to work. Are they more heat senstive than say capictors and resistors..? For Reference I purchased bulk from china if that matters. I have "Getting Started in Electronics by Forrest Mims" and I plan on buying "The Art of Electronics" as well.


kosine:
As well as books, I'd suggest having a play with LTspice. You can very quickly rig up some simple BC547 circuits and see how they respond.

I wouldn't waste time building and measuring circuits on a breadboard to begin with. Learn using spice, test the results later on.

It may also help if you go and learn about Gummel plots: http://www.eng.auburn.edu/~niuguof/multisimdev/_images/grapher_gummel.png

It's basically two logarithmic current plots. The lower one is the base current, the upper is the collector-emitter current. Pick any base voltage and the plot shows the corresponding currents. The collector-emitter current will flow through anything connected to the collector or emitter (such as resistors, LEDs etc.). From that you can then figure out the collector and emitter voltages.

Try some simple LTSpice simulations and you should see that the voltage across the transistor is whatever it needs to be to "take up the slack", so to speak.

dcbrown73:
Here is a quick tutorial on the BC547 that explains how it works and example circuit.

Good luck!

magic:
Freewheeling diode antiparallel with Q1 :wtf:

mikerj:
Semiconductors in general tend to be more sensitive to heat damage than passive components, but you have to try fairly hard to damage a bipolar transistor in a leaded package like a BC547.  That said you shouldn't need to apply the iron for more than a few seconds per lead to make a solder joint.

Chinese components are often suspect, there is a vast market in counterfeit parts that either work poorly or not at all but they tend to target the more expensive parts.  Jellybean transistors are so cheap to manufacture there would be little profit in counterfeiting them, but that's not to say it doesn't happen.

What circuit have you been trying to construct, do you have a schematic?

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