This document describes several types of logic gates: AND, OR, NOT, NAND, NOR, XOR, XNOR. It provides the logic diagram and truth table for each gate. It also gives an example of combining multiple logic gates, showing the schematic diagram and describing how to determine the output function by evaluating the circuit for each input combination in the truth table.

3. AND Gate
A circuit which performs an AND operation is shown in figure. It has n input
(n >= 2) and one output.
Logic diagram Truth Table
OR Gate
A circuit which performs an OR operation is shown in figure. It has n input
(n >= 2) and one output.
Logic diagram Truth Table

4. NOT Gate
NOT gate is also known as Inverter. It has one input A and one output Y.
Logic diagram
Truth Table
NAND Gate
A NOT-AND operation is known as NAND operation. It has n input (n >= 2) and one output
Logic diagram
Truth Table
NOR Gate

5. NOR Gate
A NOT-OR operation is known as NOR operation. It has n input (n >= 2) and one output.
Logic diagram
Truth Table
XOR Gate
XOR or Ex-OR gate is a special type of gate. It can be used in the half adder, full adder and subtractor. The
exclusive-OR gate is abbreviated as EX-OR gate or sometime as X-OR gate. It has n input (n >= 2) and one
output.
Logic diagram Truth Table

6. XNOR Gate
XNOR gate is a special type of gate. It can be used in the half adder, full adder and subtractor.
The exclusive-NOR gate is abbreviated as EX-NOR gate or sometime as X-NOR gate.
It has n input (n >= 2) and one output.
Logic diagram
Truth Table

7. 2 INPUT NAND gate
A A A B
0 0 1
0 1 0
1 0 0
1 1 1
EXNOR Gate
The 'Exclusive-NOR' gate circuit does the opposite to the EOR gate. It will
give a low output if either, but not both, of its two inputs are high. The symbol is
an EXOR gate with a small circle on the output. The small circle represents
inversion.
Schematic Symbol Truth Table
A B
ENOR
Example:

9. Block diagram

10. Below is an example of 2 input combined logic gates, now let us find the
output function for this circuit.
Truth Table Schematic Diagram
A B Q
0 0
0 1
1 0
1 1
AB
1st AND
2ndAND
OR
1st NOT
2nd NOT
AB
 First draw a 2 input truth table.
 Second let us identify the different logic gate used in the circuit. We have 2
AND gate, 2 NOT gate, and 1 OR gate.
 Third let us find the output function for the 1st combination in the truth table
A=0 and B=0.
 Input A & B goes to the 1st AND gate then have an output of0
Truth table for 1st
AND
 Input A goes to 1st NOT gate and becomes 1; input B goes to 2nd NOT gate
and becomes 1 then the inverted A & B goes to 2nd AND gate and have an
output of 1
Truth table for 2nd
AND, take note that
the inputs are inverted

11.  The output of 1st and 2nd AND gate goes to OR gate and then will have an output function of 1.
 Then the output function for Input A=0 and B=0 for this circuit is 1.
 Write the output on the truth Table.
 Repeat same process on the 2nd, 3rd, and 4th Input.
A B Q
0 0 1
0 1 0
1 0 0
1 1 1
2ndAND
OR
1stAND