2. CERTIFICATE
This is to certify that mayank chauhan of
class XII Sunflower of school Jain Bharati
Mrigavati Vidyalaya has successfully
prepared a investigatory project on “logic
gates” under the supervision of his physics
teacher Mr. Naveen Kumar sir
3. ACKNOWLEDGEMENT
This is my duty to record my sincere thanks
and deep since of gratitude to my respected
teacher. I have benefited a lot from
suggestions given to me by my school
faculty. I am indebted to my guide Mr.
Naveen Kumar sir for their constant support
4. CONTENTS
• Introduction of George boole
• Logical circuit • Logic gate
• Types of logic gates
• The NOT gate
• The AND gate
• The OR gate
• The NAND gate
• The NOR gate
• Universal logic gates
• Logic equations
• Total no. Of outputs
5. Did you know?
George Boole Inventor of the idea of logic gates due to him
only we came to know about concept of Boolean logic.
He was born in Lincoln, England and he was the son of a
shoemaker in a low class family.
George Boole,(1815-1864)
6. LOGICAL CIRCUIT “A circuit for performing
logical operations on input signals”
The three main ways of specifying the function of a combinational logic circuit
are:
1. Boolean Algebra – This forms the algebraic expression showing the operation of the logic
circuit for each input variable either True or False that results in a logic “1” output.
2. Truth Table – A truth table defines the function of a logic gate by providing a concise list
that shows all the output states in tabular form for each possible combination of input
variable that the gate could encounter.
3. Logic Diagram – This is a graphical representation of a logic circuit that shows the wiring
and connections of each individual logic gate, represented by a specific graphical.
7. LOGIC GATE
• A Logic gate might sound horribly complex, but it's simply an electric
circuit with two inputs and an output. It receives two incoming electric
currents, compares them, and sends on a new, outgoing electric current
depending on what it finds.
• The lines connected to each symbols are the inputs and outputs. • The
inputs are on the left of each symbol and the output is on the right.
• A circuit that performs a specific logic operation (eg-AND, OR) is called a logic
gate.
8. Types Of Logic Gates
• NOT
• AND
• OR
•XOR
• NAND
• NOR
•XNOR
9. THE NOT GATE OR INVERTER
• The inverter (NOT circuit) performs the operation called inversionor
complementation.
• The NOT operation changes one logic level to the opposite logical level.
When the input is Low, the output is high. When the input is high, the output
is
low.
• The inverter changes one logic level to the opposite level. In terms of bits, it
changes a 1 to a 0 and 0 to 1.
10. OPERATION OF NOT GATE
When a High level is appliedto an inverter input, a Low level will appear on its
output. When a Low level is appliedto its input, a High will appear on its output.
Timing Diagram
Truth Table
In
Out
0 1
1
Input Output
0 1 7
11. THE APPLICATION OF NOT GATE
When the temperature falls below 20c the Not gate will set on the central heating system
(cool huh).
THE AND GATE
• An AND gate can have two or more inputs and performs what is know as
multiplication.
• The output of AND gate is high when all inputs are high otherwise all outputs
are low.
12. OPERATION OF AND GATE
• An AND gate produces a HIGH output only when all of the inputs are HIGH.
When any of the inputs is LOW, the output is LOW. Therefore, the basic
purpose of AND gate is to determine when certain conditions are
simultaneously true, as indicated by High levels on all of its inputs, and
produces a High on its output.
Timing DiagramA
B
Out
Truth Table
Inputs Output
A B X 0 0 0 0 1 0 1 0 0 1 1 1
13. THE APPLICATION OF AND GATE
So while going out of the house you set the "Alarm Switch" and if the burglar enters he
will set the "Person switch", and tada the alarm will ring.
THE OR GATE
• OR gate can have two or more inputs and performs what is known as logical
addition.
• The output of OR gate is Low when all inputs are low, otherwise all outputs are
high
14. OPERATION OF AN OR GATE
• An OR gate produces a High on the output when any of the inputs is High.
The output is Low only when all of the inputs are Low. Therefore, an OR
gate determines when one or more of its inputs are High and produces a
High on its output.
Timing Diagram Truth Table
Inputs Output
A
B
Out
A B X 0 0 0 0 1 1 1 0 1 1 1 1
15. THE APPLICATION OF OR GATE
You would of course want your doorbell to ring when someone presses either the front
door switch or the back door switch..(nice).
THE NAND GATE
• The NAND gate is the one of the popular logic element because it can be
used as a universal gate; that is NAND gate can be used in combination
to perform the AND, OR, and inverter operations.
• NAND Gate is constructed by attaching NOT Gate at the output of
AND Gate, hence NAND Gate is called NOT- AND Gate.
• NAND Gate has two or more input and only one output.
16. OPERATION OF A NAND GATE
• A NAND gate produces a Low output only when all the inputs are High.
When any of the inputs is Low, the output will be High.
Timing Diagram Truth Table
A
B
Out
Inputs Output A B X 0 0 1 0 1 1 1 0 1 1 1 0
17. THE APPLICATION OF NAND GATE
FREEZER WARNING BUZZER
When the thermistor is COLD its resistance
is LARGE and the input to the NAND gate
is high.
Since the NAND gate is connected as
an INVERTER the output is LOW.
As the thermistor warms up its resistance
decreases, the voltage across it falls and
the input to the NAND gate falls.
When it becomes low enough the
output becomes HIGH and the buzzer
sounds
18. THE NOR GATE
• A HIGH output (1) results if both the inputs to the gate are LOW (0); if
one or both input is HIGH (1), a LOW output (0) results.
• NOR is the result of the negation of the OR operator.
OPERATION OF A NOR GATE
• A NAND gate produces a Low output only when all the inputs are High.
When any of the inputs is Low, the output will be High.
Timing Diagram A
B
Out
Truth Table
Inputs Output
A B A NOR B 0 0 1 0 1 0 1 0 0 1 1 0
19. THE APPLICATION OF
NOR GATE
MIXER TANK
we use a 3-input NOR gate to control the
flow of ingredients of a mixer tank.
Different kinds of ingredients are stored in
separate cylindrical Hooper. A capacitive
proximity switch is arranged outside of
each cylinder, at its bottom. This is to
detect the amount or level of ingredient.
20. UNIVERSAL LOGIC GATES
A universal logic gate is one which can implement any Boolean function
{0,1}, without the use of any other logic gate. Simply put, a logic gate which
can serve the function of ALL other logic gates, including itself.
The NAND and NOR gates are called universal logic gates because all the
other gates can be created using these two.
TOTAL NUMBER OF OUTPUTS
• To determine the total number of possible combinationof binary inputs to a
gate is determined by the following formula.
N=2n
Where N is the number of possible input
combinationsand n is the number of input
