4-4 logic gates
DESCRIPTION
logic gatesTRANSCRIPT
4.4 Logic Gates
4.4 Logic Gates
An electronics circuit with one or more inputs and a single output.Input and output can be either high (logic 1) or low (logic 0)
4.4 Logic Gates
Truth table is a table that summarises all the possible inputs and outputs of a logic gate.
4.4 Logic Gates
Boolean Algebra one form of expression which can be used to summarise the logic operation.
For example:
Logic gate NOR.
X =
The AND gate
0
0
Input Output / Q
A B
0 0 0
0
1 0 1 0
1
01 0 01 1 1
1
1
001
X = A. B
The OR gate
0
Input Output / Q
A B
0 0 0
0
0 1 1
1 0 11 1 1
0
X = A + B
The NOR / NOT- OR gate
1
Input Output / Q
A B
0 0 1
1
0 1 0
1 0 01 1 0
0
The NAND / NOT- AND gate
1
Input Output / Q
A B
0 0 11
0 1 1
1 0 11 1 0
0
Combination of logic gates
AND gate OR gate
Inputs
Logic operation Output
Inputs Logic operation
Output
A B C Q0 01 11 00 1
0
0
0 1
0 1
1
1
1 0
1 0
1
0
0
0
1
1
0
1
0
0 1
0 0 11
0 1 01
1 1 0 0
1100AND gate
0 1 0 0
0 0 11
0 1 01
1 1 0 0
1100
1 0
0 1
1010
1 0
0 0
Q
Q
Application of logic gate in control systems
Fire control system
Smoke detector
heat detector
A
B
Fire extinguisher
Fire alarm
Input Output
A B Fire extinguisher
Fire alarm
1 1
1 0
0 1
0 0