> For the complete documentation index, see [llms.txt](https://cs.brash.ca/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://cs.brash.ca/unit-1/binary-and-logic/significance-of-switching.md).

# Transistors (Changing Bits)

The most important invention in the history of computers is (arguably) the transistor. A transistor can serve two purposes:

* It can amplify a signal (transistor radio).
* It can switch on and off ridiculously fast. \
      This fast switching is what allows a computer to make decisions ***very*** fast.

<div align="center"><img src="/files/-LM_-R2_Vy-s-ERryeNd" alt="By commons.wikimedia.org/wiki/User:Inductiveload"></div>

Think of a transistor like a **`gate`** which either allows electricity through (1) or blocks it (0). If a small amount of electricity is applied to the **`base`** pin, whatever is on the **`collector`** pin is permitted through the **`emitter`** pin.

![When the base is "on" the electricity flows out the emitter](/files/-MH8q3LqcpDYYo4Y61OK)

Controlling electricity like this gives us the ability to create **`boolean logic`** or [**`logic gates`**](/unit-1/binary-and-logic/logic-gates.md).

{% hint style="info" %}

### **Consider this:**

Transistors can be made as small as $$10\text{ nanometers}$$ . That's $$0.00001 \text{ millimeters}$$.\
A typical sheet of white printer paper is about $$280,000\text{ nm}$$ thick yet a transistor can be made $$10 \text{ nm}$$. They are so small that Apple's A11 chip in the iPhone X has $$4.3 \text{ billion}$$transistors yet it is only $$88 \text{ mm}^2$$.&#x20;
{% endhint %}