Digital Electronics: Principles, Devices and Applications

Arithmetic Circuits 2637.9.1 Cascading Magnitude ComparatorsAs outlined earlier, magnitude comparators available in IC form are designed in such a way thatthey can be connected in a cascade arrangement to perform comparison operations on numbers oflonger lengths. In cascade arrangement, the A = B, A>B and AB and AB 7 . From the first-row entry of the function table it is clear that, irrespectiveof the status of other bits of the more significant comparator, and also regardless of the status of itscascading inputs, the final output produces a HIGH at the A>Boutput and a LOW at the AB 7 regardless of the status of all other comparison bits. On similar lines, thecircuit produces a valid output for any given status of comparison bits.Example 7.8Design a two-bit magnitude comparator. Also, write relevant Boolean expressions.Figure 7.37Cascading of individual magnitude comparators.