Chapter 3 Combinational Logic

CHAPTER 3 COMBINATIONAL LOGIC

Basic Combinational Logic Circuits AND-OR LOGIC



A B

B

&

X=AB+CD C

C D 

A ≥1 &

D

AND-OR-INVERT LOGIC A B C D

X=AB+CD

A B C D

& ≥1 &

Basic Combinational Logic Circuits 

Exclusive-ORLogic

A  X  =  A B +  A B

B

A

A =1 B

B

X

Basic Combinational Logic Circuits 

Exclusive-NOR Logic

A  X  =  A B +  A B

B

A B

 X  =  A B +  AB

Implementing Combinational Logic 

From Boolean Expression to a Logic Circuit 



It’s usually best to reduce a circuit to its SOP form

From a Truth Table to a Logic Circuit

Universal Property of NAND & NOR Gates 

IC are packaged with a 4 gates per  chip, buy only NAND IC and save a lots of money on inventory. One type of chip for all logic applications.

Universal Property of NAND & NOR Gates 

NAND gates as a Universal Logic Element: =

A

A B

=

A

= B

Universal Property of NAND & NOR Gates 

NOR gates as a Universal Logic Element: A

A B

= =

A

= B