Half Subtractor

Introduction

Subtractor circuits take two binary numbers as input and subtract one binary number input from the other binary number input. Similar to adders, it gives out two outputs, difference and borrow (carry-in the case of Adder). There are two types of subtractors.

  1. Half Subtractor
  2. Full Subtractor

halfsub

Truth Table

hs_truthtable

Logical Expression

Difference = A XOR B

Borrow = \overline{A}B

Implementation  

Limitation of Half Subtractor-

  • Half subtractors do not take into account “Borrow-in” from the previous circuit.
  • This is a major drawback of half subtractors.
  • This is because real-time scenarios involve subtracting the multiple numbers of bits which can not be accomplished using half subtractors.
To overcome this drawback, Full Subtractor comes into play.

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