Logic Gates

Controlling electricity gives us the ability to make yes and no decisions or true and false. By combining two signals, we can give a single true or false answer, depending on the logic. The flow of electricity is controlled using gates (no, not named after Bill Gates - like a gate).
Standard Logic Gate Symbols
NOT
AND
NAND
OR
NOR
XOR
XNOR
All Truth Tables
The simplest gate, this item inverts or reverses the signal.   Q=A‾Q= \overline AQ=A
 
Input (A)
Output (Q)
0
1
1
0
​
Only outputs true if both inputs are true.  Q=A⋅B or A×BQ = A \cdot B \text{ or } A \times BQ=A⋅B or A×B
 
A
B
Output (Q)
0
0
0
0
1
0
1
0
0
1
1
1
Any gate with a dot is an inverted gate.    Q=A⋅B‾ or A×B‾Q = \overline{A \cdot B} \text{ or } \overline{A \times B}Q=A⋅B or A×B​
 
This is the NOT AND gate:  
A
B
Output (Q)
0
0
1
0
1
1
1
0
1
1
1
0
One or the other or both!    Q=A+BQ = A+BQ=A+B
 
A
B
Output (Q)
0
0
0
0
1
1
1
0
1
1
1
1
Very simply NOT OR.    Q=A+B‾Q = \overline{A+B}Q=A+B​
 
A
B
Output (Q)
0
0
1
0
1
0
1
0
0
1
1
0
Exclusive OR meaning only one is true, not both.    Q=A⨁BQ = A \bigoplus BQ=A⨁B
 
A
B
Output (Q)
0
0
0
0
1
1
1
0
1
1
1
0
Exclusively NOT OR. If both inputs are the same, output true.    Q=A⨁B‾Q = \overline{A \bigoplus B}Q=A⨁B​
 
A
B
Output (Q)
0
0
1
0
1
0
1
0
0
1
1
1
A
B
AND
NAND
OR
NOR
XOR
XNOR
0
1
0
1
0
1
0
1
0
1
0
1
1
0
1
0
1
0
0
1
1
0
1
0
1
0
1
0
1
0
0
1
Individually:
The two "universal" gates are NOR and NAND - it is said that you can create all the other logic gates with a combination of just these two.
There are tons of videos available about logic gates. If I had to pick a favourite, my current is this one, although she talks incredibly fast and you might need to slow it down or rewind.
Transistors (Changing Bits)
Poster
Last modified 4yr ago