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Minimum number of half adders and OR gates required to build a n-bit binary adder is?

(Give circuit diagram)
asked in Digital Logic by Active (1.1k points)
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2 Answers

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2n half adder and n OR gates
answered by Junior (795 points)
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It requires (2n-1) half adders and (n-1) 2 input  OR gates

for example: for 16 bit binary (parallel) adders we require 16 Full Adders to implement

                     that implies we need  n Full adders,

                     else 1 Half Adder , 15 Full Adders  -> 1 HA,(n-1) FA

                     else  31 HA, 0 FA -> (2n-1) HA

                  for first HA we don't require  any OR gate and for the rest of the half adders we need (n-1) OR gates.

finally we need (2n-1) half adders and (n-1) OR gates
answered by (499 points)
Gotcha! For LSB we don't need 1FA right


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