CMOS Exclusive or (Xor) Using Minimum Number of Devices
Original Publication Date: 1987-Jun-01
Included in the Prior Art Database: 2005-Feb-01
The Exclusive OR (XOR) is an important logic circuit in machine architecture and is frequently used in applications, such as parity generators. The CMOS (complementary metal oxide semiconductor) circuit disclosed in this article uses a small number of field-effect transistors (FETs), four P-type and three N-type, to produce the XOR function. The CMOS XOR circuit design shown utilizes seven FET transistors to obtain a high physical chip density and a minimum delay. It operates as follows: When both inputs A and B are at an up level, transistors Q2 and Q5 are on, and output node C goes to the up level through the conduction of transistor Q5 to the up level at input node A.