This PDF provides detailed information about logic Gates.

1. Prepared by
Gayithri Ashwathreddy
Assitant professor, SKC

2. AGENDA
•Introduction to logic Gates
•Types of Logic gates
•Universal gates
•Realization of basic Gates with Universal gates.
•Implementation of logic gates with Boolean expressions

3. INTRODUCTION
•A Digital Logic Gate is an electronic circuit which makes logical
decisions based on the combination of digital signals present on
its inputs.
•Logic gates are the basic building blocks of any digital system.
• It is an electronic circuit having one or more than one input and
only one output.
•The relationship between the input and the output is based on a
certain logic.

4. TYPES OF GATES
Basic gates
Derived Gates

5. AND GATE
 It has two or more input signal but only one output signal
 If all the input signal is high(1),then the output signal is 1(high)
otherwise it is zero(0)

6. OR GATE
 It has two or more input signal but only one output signal
 If any of the input signal is high(1),then the output signal is
1(high)

7. NOT GATE
• A NOT gate has only one input and one output.
• The output state is always the opposite of the input state.
• The output is sometimes called the complement (opposite) of the input.
• NOT gate is also called as INVERTER Gate, Because the output is not
same as the input

8. BUFFER GATE
• A Buffer gate has only one input and one output.
• The output state is remains as of the input state.

9. NAND GATE
• A NAND gate has two or more input signal but only one output signal.
• The NAND gate is a complemented of AND gate.
• The output of NAND gate will be 0 only when all inputs are 1 and output
will be 0 if any input represents a 0
• NAND is short form of NOT AND

10. NOR GATE
• NOR gate has two or more input signal but only one output signal.
• The NOR gate is a complemented of OR gate.
• The output of NOR gate will be 1 only when all inputs are 0and output will
be 0 if any input represents 1.
• NOR is short form of NOT-OR

11. EXCLUSIVE OR(XOR) GATE
• An exclusive-OR has two or more input signal but only one output signal.
• Exclusive-OR gate is different form of OR gate.
• XOR gate produces output 1 for only those input combinations that
have odd number of 1’s.
• The output is 0 if there are even number of 1’s in the input.
• The output is 1 if there are odd number of 1’s in the input.

12. XNOR GATE
• The XNOR gate is complement of XOR gate.
• The output of XNOR is 1 only when the logic values of both X and Y is
same i.e. either both are equal to 1 or both are 0.
• Its output is 0 when its inputs are different.

13. UNIVERSAL GATES
•Universal gates are gates which can be used to implement
all other gates.
•This is useful as manufacturers only need to produce 1
type of universal gate to be able to use all other gates.
•The universal gates are NOR and NAND.

14. REALIZATION OF ALL BASIC GATES USING NAND GATE

15. REALIZATION OF ALL BASIC GATES USING NOR GATE

16. IMPLEMENTATION WITH LOGIC GATES
Implementation with logic gatesx
F=x+y’z

17. IMPLEMENTATION WITH LOGIC GATES
F=x’y’z+x’yz+xy’

18. IMPLEMENTATION WITH LOGIC GATES
F=xy’+x’z

19. TWO LEVEL IMPLEMENTATION
F1=y’+xy+x’yz’ F2=x(y’+z)(x’+y+z’)

20. MULTILEVEL IMPLEMENTATION