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Full Subtractor is a combinational logic circuit.
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It is used for the purpose of subtracting two single bit numbers.
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It also takes into consideration borrow of the lower significant stage.
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Thus, full subtractor has the ability to perform the subtraction of
three bits.
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Full subtractor contains 3 inputs and 2 outputs (Difference and Borrow)
as shown-
Designing a Full Subtractor-
Full subtractor is designed in
the following steps-
Step-01:
Identify the input and output
variables-
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Input variables = A, B, Bin (either 0 or 1)
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Output variables = D, Bout where D = Difference
and Bout = Borrow
Step-02:
Draw the truth table-
Step-03:
Draw K-maps using the above
truth table and determine the simplified Boolean expressions-
Step-04:
Draw the logic diagram.
The implementation of full subtractor using
1 XOR gate, 3 AND gates, 1 NOT gate and 1 OR gate is as shown below-
