LOGIC GATES
WHAT ARE LOGIC GATES?
 An electronic circuit that creates logical decision by a TRUE (ON - 1) or
FALSE (OFF - 0) representation
 Basic logic gates are:
 NOT
 AND
 OR
 More complex logic gates can be created using the basic logic gates
AND LOGIC GATE
• Output is TRUE (1) when BOTH of the inputs are TRUE (1).
Symbol:
Truth Table:
INPUTS
Boolean Expression:
Q =A & B
Q = (A)(B)
OUTPUT
A
B
Q
0
0
0
0
1
0
1
0
0
1
1
1
AND LOGIC GATE
• Output is TRUE (1) when BOTH of the inputs are TRUE (1).
Symbol:
Truth Table:
INPUTS
Boolean Expression:
Q =A & B
Q = (A)(B)
OUTPUT
A
B
0
0
0
1
1
0
1
1
Q
OR LOGIC GATE
• Output is TRUE (1) when EITHER of the inputs is TRUE (1).
Symbol:
Truth Table:
INPUTS
A
Q
B
Boolean Expression:
Q =A | B
Q =A + B
OUTPUT
A
B
Q
0
0
0
0
1
1
1
0
1
1
1
1
OR LOGIC GATE
• Output is TRUE (1) when EITHER of the inputs is TRUE (1).
Symbol:
Truth Table:
INPUTS
A
Q
B
Boolean Expression:
Q =A | B
Q =A + B
OUTPUT
A
B
0
0
0
1
1
0
1
1
Q
NOT LOGIC GATE
• Output is the inverse of the input. NOT gate is commonly called
as inverter.
Symbol:
A
Boolean Expression:
Q = A’
Q =A
Truth Table:
Q
INPUTS
OUTPUT
A
Q
0
1
1
0
NOT LOGIC GATE
• Output is the inverse of the input. NOT gate is commonly called
as inverter.
Symbol:
A
Truth Table:
Q
INPUTS
OUTPUT
A
Q
0
Boolean Expression:
Q = A’
Q =A
1