Thursday, 16 February 2012

Comparators


Comparator is a combinational circuit, which compares two binary inputs and determines when one output is greater than, less than or equal to other input.
2-bit comparator:
Logic Diagram:
 
  • For equality, XNOR logic is required, because it gives it’s output ‘1’ when both the inputs to it are equal. For 2-bit comparator both A1=B1 and A0=B0
  • A<B, if A1 is ‘0’ and B1 is ‘1’ or A1=B1 and A0=’0’ and B0=’1’
A<B=A1’B1+(A1®B1)A0’B0
  • A>B, if A1 =’1’ and B1=’0’ or A1=B1 and A0 is ‘1’ and B0=’0’
A>B=A1B1’+(A1®B1)A0B0’

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