Increasing the range of input in a 4bit adder?

Discussion in 'General Electronics Chat' started by xEnOnn, Feb 3, 2011.

  1. xEnOnn

    Thread Starter New Member

    Feb 2, 2011
    Are 1 bit full adders made up of 2 half adders, and then the say 4 bit adders made up of 4 1-bit full adders?

    Am I getting this correctly?
    Last edited: Feb 3, 2011
  2. kubeek

    AAC Fanatic!

    Sep 20, 2005
    Yes, four bit adder is 4 one bit full adders with connected Cout to Cin of the next stage.
    They say? Shouldn´t this be obvious?
  3. Papabravo


    Feb 24, 2006
    Not quite. Half-adders are not combined to make full adders. A half-adder has two inputs ( A, B ) and two outputs (S, CO). It is commonly used for the first stage in a chain of adders where there is no CARRY IN. A full-adder has three inputs (A, B, CI) and two outputs (S, CO). The full-adder is used for all the stages except the first stage because there is always the possibility of a carry in for stages 1..n, but there is no carry-in for stage 0.
  4. kubeek

    AAC Fanatic!

    Sep 20, 2005
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