In CMOS, XOR is carried out like:
_____
|
____|____
_ _| _|
A-||_ A-||_
_| _ _|
B-||_ B-||_
|_________|
|____________OUT
__|___
_ _| _|
A-||_ B-||_
|______|
__|___
_ _| _|
B-||_ A-||_
|______|
__|__
-|-
This, of course, is A
XOR B, expressed as:
_ _
(A * B) + (A * B)
A B | OUT
0 0 | 0
0 1 | 1
1 0 | 1
1 1 | 0