Combinational Circuit & Universal Gate

Combinational  Circuit

²  It is circuits with  combination of logic gates where the output depends on the current state of the inputs

²  A combinational circuit can be defined in three ways:

a) Truth table -the list of the binary value of each m output signals for each of  the 2n feasible combinations of input signal

b) Graphical symbol -the illustration of the interrelated layout of logic gates

c) Boolean equations-the expression of a Boolean function of its inputs signals for each output signal.

Simplification of  Combinational CircuitsThere are two ways to calculate Boolean expression.

Ø  Algebraic Simplification:

·          It is simplification of SOP(Sum of Product) and POS(Product of Sum)expression the identities and formula to reduce Boolean expression to one or fewer elements.

Universal Gates（NAND GATE，NOR GATE）

The  NAND  GATE

• The NAND  GATE  - a universal gate  can  use to produce the NOT, AND,
  OR and NOR function

One NAND  GATE – (inverter)

Two NAND GATE –(AND GATE)

  Three NAND   GATE –(OR GATE)

Four NAND  GATE –(NOR GATE)

THE NOR  GATE

• THE NOR  GATE –produce NOT, AND, OR and NAND Gate.
  

  One NOR GATE  – an inverter

Two NOR GATE   – OR GATE

Three NOR GATE  – AND GATE

Four NOR GATE  – NAND GATE

Written by:

Name:Chiang Han Sheng,Lim Chi Hong

No.Matrik : B031210078,B031210028