Quote:
Originally Posted by Ether
Think of the transistor as a variable resistor.
|
OK, I think I see where you're going wrong.
Think of the transistor as a water faucet. The transistor's base is the faucet knob. Just a small effort can control a huge amount of 'water'. The valve has pressurized water on one side and air on the other. As you turn the knob, water flows, and you can vary that.
Ether had it almost perfect: Think of a transistor as a
voltage-controlled resistor. (
In an electric circuit, as resistance drops, more 'current' flows). As you change the voltage on the base, the amount of resistance the transistor collector-emitter terminals have
also changes, allowing more (or less) electric current to flow.
So what a transistor is doing is taking the power from the power source and controlling how much power gets to the output. The controlling thingus is the base voltage.
The name Transistor came from a contraction of the term "transfer resistor". IN the early days, variable resistor was the best model they had to describe what these odd things did, because they were so very different from the existing technology, the vacuum tube.
(Please note that this explanation simplifies several important points of transistor operation, such as: The 'output' can sometimes be on the power-source side, the input signal is turned upside-down by some circuits, there is a narrow range of base voltages that produce a linear output, the rest have the transistor acting like a switch, and more. Folks above have covered it well)