“To verify truth table of OR,AND & NOT Gate”
“To verify truth table of OR,AND & NOT Gate”
1. Objective:
The main objective is to verify the truth table of
i. OR Gate
ii. AND Gate
iii. NOT 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. By connecting different gates in different ways we can build many circuits that perform arithmetic and other functions associated with human brain. The operation of logic gate can be understood with the help of a truth table.
Following are the basic types of logic gates
i. OR Gate
ii. AND Gate
iii. NOT Gate
3.2.1. OR 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. The interior light system of automobiles is controlled by OR Gate. Its symbol is given by:
Where A and B are the inputs and Y is the output. The mathematical expression for output Y of OR gate is given as:
Y=A+B
The truth table for OR gate is given by:
A
|
B
|
Y
|
0
|
0
|
0
|
0
|
1
|
1
|
1
|
0
|
1
|
1
|
1
|
1
|
The truth table of OR gate indicates that the output signal is one always except for the time when both the inputs are 0.
3.2.2. AND 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. Its symbol is given by:
Where A and B are the inputs and Y is the output. The mathematical expression for output Y of AND gate is given as:
Y=A.B
The truth table for OR gate is given by:
A
|
B
|
Y
|
0
|
0
|
0
|
0
|
1
|
0
|
1
|
0
|
0
|
1
|
1
|
1
|
3.2.3. NOT Gate:
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. Its symbol is given by:
Where A is the input and Y is the output. The truth table for OR gate is given by:
A
|
Y
|
0
|
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.” Current flows from the anode to the cathode and never the opposite direction. A reversed LED can keep an entire circuit from operating properly by blocking current flow.
4. Experimental Setup:
For OR Gate:
For AND Gate:
For NOT Gate:
The bread board setup for these three gate along with LED is shown below:
5. Experimentation:
To verify OR Gate:
1. First of all, a suitable IC for OR gate is chosen, i.e. IC 7432.
2. Inserted IC 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. LED is inserted on bread board with its positive terminal connected to the output pin (i.e. 3 in our case) and negative signal is given to the other terminal.
6. Initially negative signal is given to both of the input terminals i.e. 0 is the input at both terminals.
7. Hence in result output is 1 i.e. LED didn’t show light.
8. Then 0 (negative signal) is given to one terminal and 1(positive terminal) to the other. LED lights up.
9. As we are working with OR Gate, that’s why LED lights up for every input combination except 0,0.
10. Truth table is drawn.
To verify AND Gate:
1. First of all, a suitable IC for OR gate is chosen, i.e. IC 7408.
2. Inserted IC 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. LED is inserted on bread board with its positive terminal connected to the output pin (i.e. 3 in our case) and negative signal is given to the other terminal.
6. Initially negative signal is given to both of the input terminals i.e. 0 is the input at both terminals.
7. Hence in result output is 0 i.e. LED didn’t show light.
8. As we are working with AND Gate, that’s why LED didn’t light up for any input combination except 1,1.
9. Truth Table is drawn.
To verify NOT Gate
1. First of all, a suitable IC for OR gate is chosen, i.e. IC 7432.
2. Inserted IC 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. LED is inserted on bread board with its positive terminal connected to the output pin (i.e. 3 in our case) and negative signal is given to the other terminal.
6. Initially negative signal is given to both of the input terminals i.e. 0 is the input at both terminals.
7. Hence in result output is 1 i.e. LED showed light.
8. Then 1 (positive signal) is given to one terminal and 1(positive terminal) to the other. LED didn’t light up.
9. As we are working with NOT Gate, input signal is inverted every time.
10. Truth table is drawn to verify results.
6. Results & Discussion:
As we have verified the truth tables of OR, AND & NOT gate, we can deduce some main points from this. The total OR and 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 1 except the one for which both of the inputs are 0, is known to be as OR gate. OR operation or addition operation is performed via this gate. The gate which yields 1 only once for the time when both inputs are 1, Other than that it gives a zero output always, recognised to be as AND gate. NOT gate simply inverted the input operation.
7. Conclusion:
Through this experiment truth tables of OR, AND and NOT Gate are verified by using IC’s inserted on bread board along with LED to show OFF or ON status of output.
8. References:
vi. http://www.ee.surrey.ac.uk/Projects/CAL/digital-logic/gatesfunc/#notgate
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