Digital Computers Logic Gates & Applications

Digital Computers Types of Material (Electric Conductivity) – Insulator Rubber / wood – Conductor Copper / Gold / Iron / Water – Semiconductor Silicon / Germanium – Superconductor ???

Semi-Conductor Devices Wire (conductor) Resistor Diode – Electricity can go in one direction – used in rectifier (AC to DC), LEDs Transistor – used in (Logic Gates) – A voltage or current applied to one pair of the transistor's terminals changes the current flowing through another pair of terminals. – Used as Amplifier & Switching device Logic Gates – NOT,OR,AND, NOR,NAND, XOR, XNOR Integrated Circuit

Logic Gates GateSymbolTruth Table NOT Boolean ExpressionA’ or A

Logic Gates GateSymbolTruth Table OR AND

Logic Gates GateSymbolTruth Table NOR NAND

Logic Gates GateSymbolTruth Table Exclusive OR XOR Exclusive NOR XNOR

Universal Gates – NAND NPN-Transistors and Resistor

Constructing Gates with NAND

Applications of Logic Gates Computation or Processing – Half Adder – Full Adder Memory – Flip Flop

Binary Addition – Two Bits – Tree Bits

Half Adder Logic DiagramBoolean ExpressionsTruth Table

Full Adder

ABC in C out S

Full Adder

Parallel Adder