BE Lab Manual Experiment 6

 Experiment 6

Aim: - To study Half and Full Adder circuits using logic gates.

Apparatus: - Half and Full Adder kit, patch chords, Multimeter.

Theory: - In a binary system, any number can be represented with the combination of only two digits 0 and 1 as shown in the binary addition table.

 0+0=0               1+0=1

                0+1=1               1+1=0, carry =1

For Half Adder:

Fig. shows, a block symbol of Half Adder

Truth table:-

Operation:-

• The output of the X-OR gate is called the (∑) sum output while the output of the AND gate is the carry (Co).
• The AND gate produces a high output only when both inputs are high [logic 1].
• The X-OR gate produces a high output if, either of the input is, high.

For Full Adder:-

Half adder circuit is used to add two bits at a time. Full adder circuits are used for the addition of three inputs at a time giving sum and carry out.

Following fig. 1 & 2 shows the block schematic and logical diagram of the full adder.

Operation:- 

Truth table:

Consider any case of input combination.  e.g. C_in=1, B=0, A=1. Now refer to fig. (2)

Procedure:-

1. Study the circuit given on the front panel of the kit.
2. Switch ON the power supply & note that Red LED glows.
3. Measure & note the voltage for logic 1& logic 0.

For Half Adder

1. Apply the input logic combination (either 0 or 1) to A, B inputs.
2. Connect the output C₁ and S₁ to output logic indicators.
3. Verify and note down the truth table of Half Adder.

For Full Adder

1. Apply the input logic combination (either 0 or 1) to A, B & C inputs.
2. Connect the C₁ – C₂ and S₁ – S₂ using patch chords.
3. Connect the output C₀ and S₀ to output logic indicators
4. Verify and note down the truth table of Full Adder.

Observation table for Half Adder

Observation table for Full Adder

Result:-

The Truth Table for Half Adder and Full Adder circuit is verified.