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Exploration of the SWITCH nature of a transistor.
A transistor will allow or disallow current based on type. They are like on-off switches with the central wire (junction) acting as the automatic on/off switch.
When an NPN transistor has it's central wire attached to the ground, the transistor will turn off the flow of current much like a light-switch in a home. When the same central wire (or junction) receives + current, the transistor will turn on.
NPN
current in -> switch -> current out
+ = on, - = off
PNP are just the opposite. PNP will instead switch ON when their centeral wire is attached to the ground (-), and switch OFF while current is attached to +.
PNP
current in -> switch -> current out
- = on, + = off
This is where things get interesting. You can cause transistors to flop back in forth in rapid succession while making Boolean (yes/no) logical operations in order to arrive at a result based on previous switches in the circuit. A branch of mathematics called "Logic" covered under
a Discrete Mathematics course (UseFULL!!) will help one understand how to achieve one's desired results.
A colorful illustration:
NPN :
Have Bacon?
Mr. Positive Present at Switch? ?
Eat Bacon, turn on switch or just let
it flow.
If Mr. Negative comes along
Stop eating bacon and shut off
switch. Hide bacon in pocket.
PNP :
Have Bacon?
Mr. Negative Present ?
Eat bacon, leave on switch.
Observe flowing voltage.
Mr. Negative leaves and Mr. Positive
coming in (he steals bacon!)
Shut off switch and shove
remainder of bacon in mouth. Look
innocent.
I have seen "Traveling Salesman" and now hope I understand what a P=NP transistor would look like. It's something I'd like to look into when I learn more.
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