Basic logic gates, universal logic gates and derived gates (xor and xnor).

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Aim:  Study of truth tables of basic logic gates, universal logic gates, XOR and XNOR logic gates.

Material required: IC7408, IC7432, IC7404, IC7486, IC74266, A Breadboard, A Battery(5V), A LED, Connecting wires.

Theory: 
AND, OR, and NOT gates are basic gates, NAND and NOR are universal gates. Basically, logic gates are electronic circuits because they are made up of numbers of electronics devices and components. Input and Output of logic gates can occur only in two levels. These two levels are term High and Low or True and False or ON and OFF or simply 1 and 0. A table which lists all possible combinations of input and variables, and the corresponding output is called a 'truth table'. It shows the logic circuit's output respond to various combinations of logic levels at the inputs.

Procedure: 

  1. All the ICs and other components were tested.
  2. The breadboard was set-up.
  3. All combination of input and output was verified, for each logic gates.

Observation table: 


1.Basic gates - 
  • OR gate: If any input is high, output is high.
      Y = A+B
symbol of OR gate, OR gate, or gate, or logic gate
symbol of OR gate

Truth Table for OR Gate

Input A     Input B    Output
0 0 0
0 1 1
1 0 1
1 1 1
  

  • AND gate: If any input is low, output is low.
      Y = A.B

and gate, symbol of and gate, and logic gate, AND gate
symbol of AND gate


Truth Table for AND Gate

Input A    Input B     Output
0 0 0
0 1 0
1 0 0
1 1 1


  1. NOT gate: Invert the input
      Y = Ā
symbol of NOT gate, not gate, not logic gate, NOT gate
symbol of NOT gate


Truth Table for NOT Gate

Input A
Output

0
1
1
0



2.Universal gate -
  • NAND gate: Its output is high only high when one of the inputs is low.
       Y = (A.B)' / whole bar of A.B
symbol of NAND gate, NAND gate, nand logic gate
symbol of NAND gate


Truth Table for NAND Gate

Input A      Input B      Output
0 0 1
0 1 1
1 0 1
1 1 0


  • NOR gate: Its output is high only when all the input is low.
       Y = (A+B)' / whole bar of A+B
symbol of NOR gate, nor gate, NOR gate, nor logic gate
symbol of NOR gate



Truth Table for NOR Gate

Input A      Input B      Output
0 0 1
0 1 0
1 0 0
1 1 0


3.Derived gates from universal gate - 

  • XOR gate: Output is high only when odd number of inputs are high.
      Y = A⊕B

symbol of XOR gate, XOR GATE, xor gate, xor logic gate
symbol of XOR gate


Truth Table for XOR Gate

Input A      Input B       Output
0 0 0
0 1 1
1 0 1
1 1 0

  • XNOR gate: Output is high only when even number of inputs are high.
      Y = A⊙B
symbol of XNOR gate, XNOR GATE, xnor gate, xnor logic gate
symbol of XNOR gate


Truth Table for XNOR Gate

A       B       Output
0 0 1
0 1 0
1 0 0
1 1 1


Note: please search the ICs diagram on google especially on Wikipedia. I have given a diagram of OR gate Integrated circuit 7432. click the link below

NAND gate - Wikipedia

IC number of some common logic gates:

  1. AND Gate: 7408

  2. OR Gate: 7432

  3. NOT Gate (Inverter): 7404

  4. NAND Gate: 7400

  5. NOR Gate: 7402

  6. XOR Gate: 7486

  7. XNOR Gate: 74266

diagram of IC7432 i.e. of OR gate


These IC numbers are part of the 7400 series, which is widely used in digital electronics.

Result: The truth table of basic and universal (XOR and XNOR) logic gates was studied and verified.


Precautions:

  1. Make sure the apparatus is not defective.
  2. Make sure connecting wire is not loose.
  3. Never touch live wire.

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