- What is an Adder?
- What is Half Adder?
- Why is it called Half Adder?
- Truth Tables of Half Adder?
- Logics of Half Adder.
- Practical Implementation in Proteus ISIS.
- Advantages of Half Adder.
- Disadvantages of Half Adder.
AddersBefore discussing Half Adder just have a look at what are we trying to make. we describe an Adder as: " An Adder is a is a Digital Circuit that can Add two numbers, usually two Binary Numbers in Computer World" Adders can especially be designed so that can add other Number systems also. For Example, Binary Coded Decimal system, Hexadecimal system. One can use the Adders in the Circuits of Table Index Calculation, Address Coding etcetera. There are two types of Adders:
- Half Adder
- Full Adder
Half AdderFirst of all, let me Introduce the Half Adders:
"A Half Adder is a type of Adder that is the Combinational Arithmetic Circuit, having the ability to add two numbers and as a result Produces two bits, called Sum bit and Carry Bit."In School's Mathematics, we used to add two numbers by writing the numbers in the form of columns and then add the units of both the numbers with each other and followed the same procedure for tens. By the same token, Adders add two bits. We consider that adder also do so with the bits. We denote the Sum through the Greek summation symbol ? whereas, the Carry is denoted by C0 . For Example, When we add the Number 1 and 0 in different combinations, the adder add them as: 0 0 1 1 +0 +1 +0 +1
0 1 1 0 (carry=1) A half Adder can only add the number containing one bit If we use only One Gate. Hence, for a Proper working of Half Adder we need another Logic Gate that can store and work with the carry bit. For this Purpose, we use two Gates that will be describe next.
Why is it Called Half AdderWith the Name, a question pops in the mind that why we called this Circuit as Half Adder. The reason is, when we add the two numbers, we get the output that may or may not contain carry. Yet, if it has carry in it then there is no module that can save the carry for the next bit. It means, when we add two numbers, the carry is displayed, but that can no longer be used with the next bit. that is the procedure to add the two numbers, thus one can get the wrong output.
Block DiagramWe can Define the Block Diagrams as:
A Diagram of the system that Shows the Relationship of the Components by denoting the Components as blocks and the relationship between them through the flow Lines is called Block Diagram."On the Basis of above Discussion, we design the Block Diagram of Half Adder as: You can see, Half adder contains two inputs and two outputs.
Logical CircuitIn today's lesson, we'll construct the Half Adder through two simple and easy Gates named :
- XOR Gate
- AND Gate
SUM =A XOR Band for Cary bit, we use AND Gate
CARRY=A AND BLet's move towards the Practical implementation of Circuit of Half Adder in Proteus ISIS.
Designing of Half Adder in Proteus ISISTo design the circuit of Half Adder, we need the following Devices: Material required:
- AND Gate.
- XOR Gate.
- Logic toggle.
- Ground Terminal.
- Connecting Wire.
- Choose the first four components from the Pick Library Button Labeled as 'P'.
- Arrange the XOR Gate above and AND gate just below the XOR Gate.
- Connect the Logic Toggles on the Inputs of XOR Gate.
- Join the inputs of AND Gate with the Inputs of XOR Gate.
- Connect the LEDs with the output Terminals of both Gates.
- Add the ground terminal with both the LEDs.
- The Circuit should look like this:
Advantages of Half Adder
- Half Adders are the Basic basic Building Blocks to learn 1 bit addition.
- They are simple in Construction.
- Half Adders are easy to use.
- We can Get a Half Subtractor mere inverting the Circuit.
Disadvantage of Half Adder
- There is no mechanism to use the carry in the next addition.
- Can perform very specific functions.
- It may give the wrong output.