Digital Logic

Binary numbers and Voltage Levels

Binary digits are 0 and 1. In digital logic these two digits are use to represent two voltage levels. 

Signals in digital electronics have two distinct voltage levels with built-in tolerances for variations in the voltage

A valid digital signal should be within either of the two shaded areas

AND gate

Boolean Expression

X = A . B

Logic Diagram Symbol

Truth Table

OR gate

Boolean Expression

X = A + B

Logic Diagram Symbol

Truth Table

Tri-state buffer

Inverter

Boolean Expression

X = A'

Logic Diagram Symbol

Truth Table

XOR gate

Boolean Expression

Logic Diagram Symbol

Truth Table

NAND Gate

Boolean Expression

X = (A . B)'

Logic Diagram Symbol

Truth Table

NOR gate

Boolean Expression

X = (A + B)'

Logic Diagram Symbol

Truth Table