13-04-2013, 04:19 PM
IMPLEMENTATION OF FULL ADDER AND FULL SUBTRACTOR CIRCUITS
AIM:
To design and implement the full adder and full subtractor using digital logic gates.
THEORY:
The most basic arithmetic operation is the addition of two binary digits. There are four
possible elementary operations, namely,
0 + 0 = 0
0 + 1 = 1
1 + 0 = 1
1 + 1 = 102
The first three operations produce a sum of whose length is one digit, but when the last
operation is performed the sum is two digits. The higher significant bit of this result is called a
carry and lower significant bit is called the sum.
FULL ADDER:
A full adder is a combinational circuit that forms the arithmetic sum of input; it consists of three inputs and two outputs. A full adder is useful to add three bits at a time but a half adder cannot do so. In full adder sum output will be taken from XOR Gate, carry output will be taken from OR Gate.
FULL SUBTRACTOR:
The full subtractor is a combination of XOR, AND, OR, NOT Gates. In a full subtractor the logic circuit should have three inputs and two outputs. The two half subtractor put together gives a full subtractor .The first half subtractor will be C and A B. The output will be difference output of full subtractor. The expression AB assembles the borrow output of the half subtractor and the second term is the inverted difference output of first XOR.
PROCEDURE:
1. Connections are given as per the circuit diagram on the bread board.
2. The power supply is switched ON and set a voltage of 5 Volts.
3. If the input to be given to a gate is logic ‘1’ then it is connected to +5 Volts and if the input to be given to the gate is logic ‘0’ then the particular input terminal is connected to ground.
4. Truth tables of full adder and full subtractor are verified.
5. If the output is logic ‘1’ then the LED glows, if the output is logic ‘0’ then the LED does not glow.