Transistors are solid state switches. It acts like an electromechanical switch, but without the moving part. This is possible because of the [silicon](https://en.wikipedia.org/wiki/Silicon) properties, which is semi conductor. At the atomic level, an atom of silicon has 4 electrons. We introduce impureties in the silicon : an atom of [boron](https://en.wikipedia.org/wiki/Boron), with 3 electrons, that cause a positively charged one, called P-type, because electrons from other atoms are constantely moving through atoms to fill the gap, called a hole, making the current flow (current flow is only electrons moving). N-Types are made introducing atoms of [phosphorus](https://en.wikipedia.org/wiki/Phosphorus), that have 5 electrons,* "doping"* the silicon, so it is negatively charged and where the current don't flow. The most basic transistor is made of a combination of two N-Types silicons, and a P-Type silicon. The emitteur and the collecteur are N-Types silicons, and the gate, the P-Type silicon. This create *"negative depletion layers"* that prevent the electrons moving from the emitteur to the collecter, because the negative charges are repealing each others. By applying a positive current to the gate, all the silicons are positively charged, leting the electrons move from the emitter to the collecter and thus the current flow. This is the exact same thing as switches, with the difference that, in electromechanical switches, applying current to the get create a magnetic field that stick the metal piece use as a bridge between the emitter and collecter to allow the current to pass. This mecanichal part is becomming a problem when you want to perform high speed operation, such as opening/closing a circuit several time per second. This is where transistors are useful: - They're more reliable as there is no moving part - They're more efficient, as electrons moves at about the speed of light, operation can take way less time - Really good manufactured transistors can be switched around every 15 nanoseconds : There is 1 000 000 000 nanoseconds in a second, so it means that a transistor could switch 66 666 666 times per second. 🤯 Transistors are the most basic [electronics](Electronics.md) components used to create [logic gates](Logic%20gates.md). As computers are made of milions of logic gates, there is bilions of transistors at a very small scale. Transistors are the most abondous manufactured object ever made in the entire history of humanity. ## Links : - [How does a transistor work?](https://www.youtube.com/watch?v=IcrBqCFLHIY) - [Transistors - The invention that changed the world](https://www.youtube.com/watch?v=OwS9aTE2Go4) - [Transistors - Electronics Basic 22](https://www.youtube.com/watch?v=OwS9aTE2Go4) - [How fast do transistors switch on and off?](https://www.reddit.com/r/AskElectronics/comments/3p9wlo/how_fast_do_transistors_switch_on_and_off/) - [Convert nanoseconds to seconds](https://www.calculateme.com/time/nanoseconds/to-seconds/) - [Periodic table](https://en.wikipedia.org/wiki/Periodic_table#Alkali_metals,_Alkaline_earth_metals)