This presentation introduces logic gates. It defines a logic gate as a building block of digital circuits that takes two or more inputs and outputs one value based on Boolean algebra. Common logic gates are then described, including AND, OR, and NOT gates. NAND and NOR gates are universal gates that can be used to represent all other logic functions. Exclusive gates like XOR and XNOR are also discussed. Finally, compound gates are defined as combinations of basic logic gates to form more complex functions.

1. WELCOME TO MY PRESENTATION
Assalamulaikum
Md. Nazrul Islam
B.Sc in CSE
University of Chittagong

2. Contents of Presentation
 What is logic gate?
 Why it is used?
 Basic logic gates
 Universal logic gates
 Universality of NAND & NOR gate
 Exclusive logic gates
 Compound or Complex logic gate

3. Logic Gate:
A logic gate is a building block of a Digital Circuit which
takes two or more inputs and gives only one output
based on Boolean algebra.
Use of logic gates
Logic circuits include such devices as
multiplexers, registers, arithmetic logic units(ALUs),
and computer memory, microprocessors, Integrated
circuits, discrete electronic components, simple switches,
relays, hydraulic etc.

4. Kinds of logic gates
1.Basic logic gate
2.Universal logic gate
3.Exclusive gate
4.Compound or complex gate

5. Basic logic gate
1. AND GATE
 AND gate is an electronic circuit which is used for Boolean algebra or
logical Multiplication .
 If two input A,B and output isY .Then we get
Y = A AND B
=A.B
=AB

6. AND gate
 It gives a high output (1) only if all its inputs are high.
 If A&B two sets then we can define “AND” operation by
Venn diagram. It would be like this.

7. AND gate
The wave form ofAND gate for two input A&B..
A
B
Y
Three input AND gate

8. 2.OR gate
 OR gate is an electronic circuit which is used for Boolean
algebra or logical summation.
If two input A,B and output isY .Then we
get
Y = A OR B
=A+B

9. 2.OR gate
 It gives a high output (1) if one or more of its inputs are
high.
If we represent the “OR GATE” ByVenn Diagram then
we can see thus

10. 2.OR gate
 The wave form of “OR” gate for two input A&B..
Three input OR gate

11. 3.NOT gate
 “NOT” gate is an electronic circuit which is used for Complement
work.
 Its also called “Inverter”.
 It contains 1 input and 1 output. If input is 1 then output will be 0,and
if input is 0 then output will be 1.
If 1 input is A and output is Z .Then we get
Z = NOT A
=VAROF A

12. 2.Universal Logic gate
(I) NAND gate:
 NAND gate consist of AND + NOT gate.
 The outputs of all NAND gates are high if any of the
inputs are low.
If 2 input is A ,B and output is Z .Then we get
Z = NOT (A and B)
=VAROF ( A.B)
Venn Diagram

13. 2.Universal Logic gate(NAND)
Universality of NAND
NAND gate
NOT gate
NAND gate AND gate
OR gate

14. 2.Universal Logic gate
(II) NOR gate:
 NOR gate consist of OR + NOT gate.
 The outputs of all NOR gates are low if any of the inputs
are high.
If 2 input is A ,B and output is Z .Then we get
Z = NOT (A+B)
=VAROF ( A+B)

15. 2.Universal Logic gate(NOR)
Universality of NOR

16. 3.EXCLUSIVE gate
(I) XOR gate
XOR gate is a digital logic gate that gives a true (1
or HIGH) output when the number of true inputs is
odd.
TruthTable

17. 3.EXCLUSIVE gate
(II) XNOR gate
The XNOR gate is a digital logic gate whose
function is the logical complement of the exclusive
OR (XOR) gate.
TruthTable

18. 4.Compound or Complex gate
Compound logic gates (sometimes Complex
logic gate) are simple devices that function like a
few basic logic gates combined.
It would be many types.Such as:
1.AND-OR-Invert (AOI)
2.OR-AND-Invert (OAI)
2-1 AOI