05-04-2012, 09:39 AM
HIGH SPEED ADDER USED IN DIGITAL SIGNAL PROCESSING
HIGH SPEED ADDER USED IN DIGITAL SIGNAL PROCESSING.pptx (Size: 355.25 KB / Downloads: 59)
INTRODUCTION
Among the various arithmetic operation addition is the simplest operation.
A combinational circuit that performs the addition of two bits known as half adder.
And that performs the addition of three bits known as full adder.
A full adder can be implemented from two half adders
FULL ADDER
This simple adder has some draw back.
It is slow and it will not produce the correct result unless the signals are given enough time to propagate through the gates connected from the inputs to the outputs.
The solution for reducing the delay of the circuit is to employ faster gates with reduced delays.
There is some other adder, which takes minimum time to perform the addition operation.
These are-
Ripple Carry Adder
Carry Look Ahead Adder
Carry Select Adder
2’s Complement Adder
Conditional Sum Adder
Carry Save Adder
RIPPLE CARRY ADDER
In a ripple-carry adder the result of an addition of two bits depends on the carry generated by the addition of the previous two bits. Thus, the Sum of the most significant bit is only available after the carry signal has rippled through the adder from the least significant stage to the most significant stage
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In the ripple carry adder, the addition of (1+1 = 102) in the least significant stage causes a carry bit to be generated. This carry bit will consequently generate another carry bit in the next stage, and so on, until the final carryout bit appears at the output.
As a result, the final Sum and Carry bits will be valid after a considerable delay
CARRY LOOK AHEAD ADDERS
For first addition operation the most widely used is the principle of look-ahead carry.
Adder design with this consideration in mind are called high speed adder.
APPLICATION
RCA:
These are the adder that can add faster
by using more hardware.
It is used to construct a logic circuit that
can add N-bit numbers.
CONCLUSION
Most of the adder structures discussed in this paper are applicable to general-purpose designs, with a few exceptions.
This paper has presented a comprehensive comparison of the six most commonly used adder structures.
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A detailed analysis of the area requirement, the maximum operational speed and the power consumption has provided a convenient way to compare the advantages and trade-offs of each design. Thus, the adder best suited to any given design may be easily selected using the data presented.
REFERENCE
MANO, M. M. AND C. R. KIME.“Logic and Computer Design Fundamentals”,4th ed.
Gutub, A. and Tahhan, H."Improving Cryptographic Architectures by Adopting Efficient Adders in their Modular Multiplication Hardware"