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The half adder adds two single binary digits. It has two outputs, sum (S) and carry (C). The carry signal represents an overflow into the next digit of a multi-digit addition.
A→0
B→1 +
--- 1
A→0 B→0 + --- 0
A→0 B→1 + --- 1
A→1 B→0 + --- 1
A→1 B→1 + --- 10
INPUT OUTPUT
A B SUM SOP CARRY SOP
0 0 0 0
0 1 1 A’B 0
1 0 1 AB’ 0
1 1 0 1 A.B
SUM=A’B+AB’ →XOR
CARRY=A.B
Half adder logic diagram
Full adder The full adder adds two multiple binary digits. full-adder has three inputs and two outputs. The first two inputs are A and B and the third input is an input carry designated as Carry In. When a full adder logic is designed, we will be able to string eight of them together to create a 8- bit adder and cascade the carry bit from one adder to the next. The carry is designated as Carry Out and the sum is designated as Sum.
Combinational vs Sequential circuits Combinational circuits: Output depends only on the input of that time, Sequential Circuit: Output depends
not only on the present inputs but also on the previous inputs and outputs. This type of circuit is required
to perform sequence of actions without getting any further inputs. Use for memory storage (SRAM)
No. Key Combinational Circuit Sequential Circuit 1 Definition Combinational Circuit is the type of
circuit in which output is independent of feedback of previous output and only relies on the input present at that particular instant.
On other hand Sequential circuit is the type of circuit where output not only relies on the current input but also depends on the previous output.
2 Feedback In Combinational circuit as output does not depend on the feedback, no feedback is required for its next output generation.
On other hand in case of Sequential circuit output relies on its previous feedback so output of previous input is being transferred as feedback used with input for next output generation.
3 Performance As the input of current instant is only required in case of Combinational circuit, it is faster and better in performance as compared to that of Sequential circuit.
On other hand Sequential circuit are comparatively slower and has low performance as compared to that of Combinational circuit.
4 Complexity No implementation of feedback makes the combinational circuit less complex as compared to sequential circuit.
However, on other hand implementation of feedback makes sequential circuit more complex as compared to combinational circuit.
5 Elementary Blocks
Elementary building blocks for combinational circuit are logic gates.
On other hand building blocks for sequential circuit are flip flops.
6 Operation Combinational circuit are mainly used for arithmetic as well as Boolean operations.
On other hand Sequential circuit is mainly used for storing data.
FLIP FLOPS Flip flops are actually an application of logic gates. With the help of Boolean logic, you can create memory
with them. Flip flops can also be considered as the most basic idea of a Random-Access Memory. When a
certain input value is given to them, they will be remembered.