Lecture 22 : Logical Effort Calculation of few Basic Logic Circuits
22.5 Logical Effort of a XOR Gate
A two input XOR gate is shown in figure 22.5.
Here we will calculate the logical effort for a bundle (A* or B*) instead of only one input
as complementary inputs are applied.
Logical effort for a bundle A is g = (2+4+2+4)/ (1+2) = 4.
Logical effort for a bundle B is g = (2+4+2+4)/ (1+2) = 4.
Fig 22.4: XOR Gate
22.6 Examples Circuits
Example Circuit 1:
Example Circuit 2: 4 BIT MUX
Example 1:
Example2:
Logical effort for input D is gD = (2+4)/ (1+2) = 2
Logical effort for bundle S is gs =(2+4)/ (1+2) = 2.
For one arm, g = 12/3 = 4
For N-way symmetrical MUX g= 4N (this is for the static CMOS MUX
only)
