Basis of logic gates

This post is about logic gates, those one are the basis of calculation in base 2 (so also of computers).
In this post I'll talk about three logic gates:
-not
-and
-or

NOT Gate
The not gate return the opposite of the input. Here is the truth table:
in out
0   1
1   0

This is the standard symbol of NOT gate:

AND Gate
The and gate return positive just if all the inputs are positive. Here is the truth table:
a b out
0 0   0
0 1   0
1 0   0
1 1   1

This is the symbol of AND gate:
 

OR Gate
The or gate return positive just if one input is positive. Here is the truth table:
a b out
0 0   0
0 1   1
1 0   1
1 1   1

This is the symbol of OR gate:

This gates can be created using transistors like BC547, here is a short summary about logic gates made using transistors:

 

You can also download a pdf of this summary here.

Here are some photos of logic gates made using transistors:

 

I hope you like this post, if you have any question comment or send me an email to damianoandre@gmail.com

Bye, Dami