“To design & verify truth table of NOR & NAND Gate”
“To design & verify truth table of NOR & NAND Gate”
1. Objective:
The main objective is to design and verify the truth table of
i.
NOR Gate
ii.
NAND Gate
2. Components:
i.
Bread
Board
ii.
Connecting
Wires
iii.
LED
iv.
Battery
v.
3 IC’s
a. IC 7432 for OR Gate
b. IC 7408 for AND Gate
c. IC 7404 for NOT Gate
3. Introduction:
3.1.Bread Board:
A
bread board is an electronic board into which the electrical components like
diodes and resistors are placed. The sockets of bread board are sturdy and
rugged. Diodes or other electrical components should be placed without making
any damage to the board.
3.2.Logic Gates:
Logic gates
are the basic building blocks of any digital system. It is any electronic
system having one or more input and only one output. The relationship between
input and output is based on some logic. At any given moment every terminal is
at one of two binary conditions 0 or 1.
Following are
the logic gates which we are going to design in this experiment:
i.
NOR Gate
ii.
NAND Gate
3.2.1.
NOR Gate:
NOR gate is a
combination of OR and NOT gate. An OR Gate is a logic gate that has two or more
inputs and one output terminal that perform logical disjunction. The output of
an OR Gate is true or 1 if one or more inputs are true or 1. The OR Gate
performs mainly the addition operation. NOT Gate is a logic gate which produces
inverted result at its output. NOT Gate has one input and one output terminal.
The inverter changes one logic level to its opposite. The symbol of NOR gate is
shown below:
The truth table
for NOR gate is given by:
A
|
B
|
Y
|
0
|
0
|
1
|
0
|
1
|
0
|
1
|
0
|
0
|
1
|
1
|
0
|
The truth
table of NOR gate indicates that the output signal is one only for the time
when both the inputs are 0.
3.2.2.
NAND Gate:
NAND gate is a combination of AND & NOT
gate. AND Gate is a logic gate having two or more inputs and one output. If all
the inputs are at 1 then only in that case that output of gate is one. The AND
Gate performs logic multiplication usually known as AND function. NOT Gate is a logic
gate which produces inverted result at its output. NOT Gate has one input and
one output terminal. The inverter changes one logic level to its opposite.The
symbol for NAND gate is shown below:
The
mathematical expression for output Y of AND gate is given as:
The truth
table for NAND gate is given by:
A
|
B
|
Y
|
0
|
0
|
1
|
0
|
1
|
1
|
1
|
0
|
1
|
1
|
1
|
0
|
3.3.Integrated Circuits:
A circuit of transistors, resistors, and capacitors constructed on a single semiconductor wafer or chip, in which the components areinterconnected to perform a given function. IC’s consume very little current, generate comparatively
little heat, and are far more shock-proof and reliable than the older
discrete-component circuits.
An integrated circuit consists of a number of circuit components (e.g. transistors, diodes, resistors
etc.) and them inter connections in a single small package to perform a
complete electronic function. These components are formed and connected within
a small chip of semiconductor material. IC’s can be used as advanced logic
gates. Some IC’s description is given below which can be used for logic gates.
No.
|
Description
|
7400
|
Quad two-input NAND gate (four NAND
gates)
|
7402
|
Quad two-input NOR gate (four NOR
gates)
|
7404
|
Hex inverter (six NOT gates)
|
7408
|
Quad two-input AND gate (four AND
gates)
|
7432
|
Quad two-input OR gate (four OR
gates)
|
7486
|
Quad two-input XOR gate (four XOR
gates)
|
3.4.Light Emitting Diodes:
A light-emitting diode (LED) is a semiconductor device that emits visible
light when an electric current passes through it. LED’s
convert electrical energy to light energy. In electronics, polarity indicates whether a circuit component is symmetric or not.
Being diodes, will only allow current to flow in one direction. And when
there’s no current-flow, there’s no light. The positive side of the LED is
called the “anode” and is marked by having a longer
“lead,” or leg. The other, negative side of the LED is called the “cathode.”
4. Experimental Setup:
The experimental setup for NOR & NAND is same with the difference
only in the combination of IC’s.
5. Experimentation:
To design & verify NOR Gate:
1. First of all, suitable IC’s for OR and NOT
gate are chosen, i.e. IC 7432 & 7404 respectively.
2. Inserted IC’s on the bread board.
3. As there are 14 pins on IC, 7th
pin is grounded and a positive potential is applied to the 14th pin
via a battery of potential less than 5V.
4. Input signal is given to the input pins, i.e.
1 & 2 in our case through a battery
5. Output terminal ( pin 3) is connected with
the input pin of NOT gate.
6. LED is inserted on bread board with its
positive terminal connected to the output pin (i.e. 2 in our case) of NOT gate and
negative signal is given to the other terminal.
7. Initially negative signal is given to both of
the input terminals i.e. 0 is the input at both terminals.
8. Hence in result output is 1 i.e. LED lights
up.
9. Then 0 (negative signal) is given to one
terminal and 1(positive terminal) to the other. LED didn’t light up.
10. As we are working with NOR Gate, that’s why
LED lights up for only input combination of 0,0.
11. Truth table is drawn.
To verify AND Gate:
1. First of all, a suitable IC for AND & NOT
gate is chosen, i.e. IC 7408 & 7404 respectively.
2. Inserted IC’s on the bread board.
3. As there are 14 pins on IC, 7th
pin is grounded and a positive potential is applied to the 14th pin
via a battery of potential less than 5V.
4. Input signal is given to the input pins, i.e.
1 & 2 in our case through a battery
5. Output terminal ( pin 3) is connected with
the input pin of NOT gate.
6. LED is inserted on bread board with its
positive terminal connected to the output pin (i.e. 2 in our case) of NOT gate and
negative signal is given to the other terminal.
7. Initially negative signal is given to both of
the input terminals i.e. 0 is the input at both terminals.
8. Hence in result output is 1 i.e. LED lights
up.
9. As we are working with NAND Gate, that’s why
LED didn’t light up foronly input combination 1,1.
10. Truth Table is drawn.
6. Observations & Calculations:
The truth table for NOR gate which we have observed is shown below:
A
|
B
|
Y
|
0
|
0
|
1
|
0
|
1
|
0
|
1
|
0
|
0
|
1
|
1
|
0
|
The truth table for NAND gate which we have observed is shown below:
A
|
B
|
Y
|
0
|
0
|
1
|
0
|
1
|
1
|
1
|
0
|
1
|
1
|
1
|
0
|
7. Results & Discussion:
We have designed NOR and NAND gate by combining NOT & OR and NOT
& AND gate respectively. As we have also verified the truth tables of NOR
& NAND gate, we can deduce some main points from this. The total OR &
AND logic gates in IC’s 7432 & 7408 respectively are 4, and 6 NOT logic
gates in IC 7404. The logic gate whose all output entries are 0 except the one
for which both of the inputs are 0, is known to be as NOR gate. OR operation or
addition operation is performed along with the NOT operation via this gate. The
gate which yields 0 only once for the time when both inputs are 1, Other than
that it gives a zero output always, recognised to be as NAND gate. NOT gate
simply inverted the input operation.
8. Conclusion:
Through this experiment we have designed NOR and NAND gate and truth
tables of NOR & NAND Gate are verified by using IC’s inserted on bread
board along with LED to show OFF or ON status of output.
9. References:
I.
http://logic.ly/lessons/nor-gate/
IV.
http://whatis.techtarget.com/definition/logic-gate-AND-OR-XOR-NOT-NAND-NOR-and-XNOR
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