The document provides an overview of logic gates, which are fundamental components in digital circuits that implement logical operations on binary signals. It covers the basic gates such as AND, OR, NOT, as well as their respective truth tables, operational principles, and examples of their configuration using switches and LEDs. Additionally, it discusses other gates like NOR, NAND, XOR, and XNOR, explaining their functions through truth tables and Boolean equations.

2. INTRODUCTION
• Logic gates are the actual physical implementations of the
logical operators.
• These gates form the basic building blocks for all digital logic
circuits.
• Logic gates process signals which
represent true or false.
Logic States
True False
1 0
High Low
On Off
+Vs -0V

3. TRUTH TABLE
• A truth table is a means for describing how a logic
circuit's output depends on the logic levels present
at the circuit's inputs.
Input A
Output X
Input B
A B X
Low Low ?
Low High ?
High low ?
High High ?

4. LOGIC GATES
BASIC LOGIC
GATES
AND
OR
NOT
OTHER LOGIC
GATES
X-OR
X-NOR
UNIVERSAL LOGIC
GATES
NAND
NOR

5. 5
v
The NOT gate is the first of the three fundamental logic
gates.
The NOT Gate (inverter):
Input A Output
X
A X
0 1
1 0
Truth Table: Is a chart that lists the input condition on the left
and the gate’s output response on the right. The table shows
that the NOT gate responds at the output with the inverse of
the signal applied to the input.
In order to see how it works, the gate has been connected to a
switch and LED. Continue to see the system in action…
Logic 1
OFF
Logic 0
ON
Logic 1
OFF
Logic 0
ON
Logic 1
OFF
Logic 0
ON

6. The OR Gate:
The OR gate is the second of three fundamental logic gates.
Truth Table: The table shows that the OR gate responds with
a high at the output if the signal applied to the input A or B
is high.
Input A
Output
XInput B
OR
5
v
5
v
5
v
In order to see how it works, the gate has been connected to 2
switches and LED. Continue to see the system in action…
Logic 0
Logic 0
Logic 0
Logic 0
Logic 1
Logic 1
Logic 1
Logic 1
Logic 0
Logic 1
Logic 1
Logic 1
A B X
0 0 0
0 1 1
1 0 1
1 1 1

7. The AND Gate:
The AND is the last of the remaining fundamental logic gates.
Truth Table: The table shows that the AND gate responds with a high at
the output if the signal applied to the input A and B are both high.
5
v
5
v
5
v
Input A
Output
X
Input B
AND
In order to see how it works, the gate has been connected to 2
switches and LED. Continue to see the system in action…
Logic 0
Logic 0
Logic 0
Logic 0
Logic 0
Logic 1
Logic 1
Logic 0
Logic 0
Logic 1
Logic 1
Logic 1
A B X
0 0 0
0 1 0
1 0 0
1 1 1

8. Logic 1
Logic 0
Logic 0
Logic 0
Logic 0
Logic 1
Logic 1
Logic 0
Logic 1
NOR Gate:
The NOR gate is equivalent to an OR gate with a NOT gate connected to
its output. NOR comes from the words Not OR. Continue to see the
standard symbol for NOR.
Input A
Output
XInput B
NOR
5
v
5
v
5
v
Logic 0
Logic 1
Logic 0
In order to see how it works, the gate has been connected to 2 switches and
LED. Continue to see the system in action…
BAX Boolean Equation: here is the equation for the
NOR gate.
A B X
0 0 1
0 1 0
1 0 0
1 1 0
NOR Symbol
Truth Table: The table shows that the NOR gate responds with a low at
the output if the signal applied to the input A or B is high.

9. 5
v
5
v
5
v
Logic 1
Logic 1
Logic 0
Logic 0
Logic 1
Logic 1
Logic 1
Logic 0
Logic 1
NAND Gate:
The NAND gate is equivalent to an AND gate with a NOT gate connected to its
output. NAND comes from the words Not AND. Continue to see the standard
symbol for NAND.
Input A
Output
XInput B
NAND
Logic 0
Logic 1
Logic 0
In order to see how it works, the gate has been connected to 2
switches and LED. Continue to see the system in action…
BAX Boolean Equation: here is the equation for the
NAND gate.
A B X
0 0 1
0 1 1
1 0 1
1 1 0
NAND Symbol
Truth Table: The table shows that the NAND gate responds with a low
at the output if the signal applied to the input A and B is high.

10. X-OR Gate
The X-OR gate is an exclusive OR gate. It will output a logic 1 if there is an
exclusive logic 1 at input A or B. Exclusive means: Only one input can be high at
one time.
Input A
Output
XInput B
X-OR
BAX 
X-OR Boolean Equation:
A B X
0 0 0
0 1 1
1 0 1
1 1 0
The X-NOR gate is an exclusive OR gate with an NOT gate at the output. It will
output a logic 0 if there is an exclusive logic 1 at input A or B.
A B X
0 0 1
0 1 0
1 0 0
1 1 1
Input A
Output
XInput B
X-
NOR
X-OR Boolean Equation:
BAX 
X-NOR Gate