It can be an amplifier or a switch, but today let’s put down notes about switches because I found them more interesting: Silicon is a semiconductor 4 valence electrons Tetrahedral crystal Doping a semiconductor n-type doping: injecting a small amount of an element like Phosphorus, which is similar to silicon and has 5 valence electrons. Having one more than silicon makes the conductivity better it’s the negative electrons that move p-type an element with 3 valence electrons like Boron. That way it creates a hole that also increases the conductivity, because the electrons can move into the hole itself the hole, which is a lack of an electron, actually acts like a positive charge, and that’s why it’s the “P” type. The movement here is of the holes themselves By the way, that doesn’t mean they are actually positive and negative, but neutral, because of the number of electrons and protons inside Transistor are made of P-Type and N-Type doping Figure 1 - Transistor built from P-type and N-type doping ...