4 ms·
Here is how I explain it. Transistors use a small current to control a larger current. You can think of this as one person tapping another on the shoulder of a
by westcort 4y ago
Here is how I explain it.
Transistors use a small current to control a larger current. You can think of this as one person tapping another on the shoulder of another person. But what good is that? Not much, on its own.
It is only possible to use this property to store data because you can build a circuit called a flip flop https://en.wikipedia.org/wiki/Flip-flop_(electronics) https://en.wikipedia.org/wiki/Flip-flop_(electronics) that enables 2 pulses of current to translate into 1 pulse of current.
That may not seem like much, but it enables everything happening in modern digital technology.
So how does it work?
Let's say you have 5 people in front of you, in a line. Everyone in line is directed to tap once on the next person for every 2 taps on their shoulder. So, for you, you feel 2 taps, and then you tap once. This is what a flip flop does.
Now, you get an additional instruction. When you are tapping with your left hand, you raise your right hand and when you are not tapping with your left hand, you lower your right hand.
Now, for every tap of the first person, the next person taps half as often, and the next person in line taps half as often, etc.
If everyone keeps time, looking at the group of people, you will see raised arms and lowered arms. The raised arms are 1s and the people without raised arms are 0s. Now you are counting in binary.
In a digital clock, this process is used to translate a quartz crystal's pulses into counting seconds and time. The same process can also be used to store numbers. For example, let's say I have 25 flip flops in series. Now, I can store a number as large as 2^25 in memory.
- sbf501 4y agoNice. But that's a BJT in saturation or cutoff. Which is only part of the story. The magic of a BJT is in quiescent region, which is like using a crowbar to lift something really heavy: the lever amplifies your force the same way a little base current amplifies the Emitter/Collector current. Going further, a mosfet doesn't use current to switch, it uses electric field. I like to say: The charge that builds up on the gate from the applied voltage causes a depeletion(enhancement) region which is like Moses parting the red sea, so that holes/electrons can move through it.
- capn_duck 4y agoYou're talking about the role that transistors play as switches in a digital logic circuit. The video is about the physical operation of, in particular, bipolar junction transistors, which are more commonly used as amplifiers.