modified 8 years ago

Playing with NPN confused.

00:36:14

Not quite sure I understand the differences here, even though I can manipulate them predictably. Anyone able to explain? Why the base required more resistance in one than the other?

published 8 years ago

Joben28

8 years ago

Well, correction: I understand the base voltage is different, but why does the order of the LED in series matter?

dblackfired

8 years ago

Second your example. You could put the same power supply on collector in serie with resistor on base

dblackfired

8 years ago

To power a led. You will always need a resistor in serie. To limit his current. Above 2v

dblackfired

8 years ago

Resistor on base is to limit current on base. Not supplying above mA. Always uA

dblackfired

8 years ago

Transistor can be used as a switch. If voltage across resistor stay with all the voltage. It is 0 logic

dblackfired

8 years ago

If voltage on base get at least 0.6-0.7V it get power on the transistor

BillyT

8 years ago

You have not done your self any favours in your circuit layout, I don't know why people do it, particularly those just starting. Use the components as they come down from the selection bar, that is by convention how they are normally used and presented. I have re-arranged your circuit into normal perspective, if you now look at them you can see what is happening. http://everycircuit.com/circuit/5335945904914432

Joben28

8 years ago

BillyT, you're right. That is more pleasant to see -- and easier. I updated this schematic according to yours shown. Thanks.

BillyT

8 years ago

Now that you have done that, can you see what happens when the base voltage is greater than the emitter voltage? Tip, check the amount and direction of current flows. Also change the voltages over, but make the base voltage 3V, because the collector voltage can only be the base voltage minus about 0.75V. make the base resistor about 750 Ohms. Watch what happens as you make each change. Bottom line, a emitter circuit is normally a voltage amplifier, and a collector circuit is basically a current amplifier.

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