lesson 2

Lessons: IC’s and Gates

Priscilla M. SoteloInstructor, Digital Design Lab

Inspiration Motivation Lesson Proper Assignment/

Announcement/Reminders

Agenda

“The only way to do great work is to love what you do,” says Steve Jobs. “If you

haven’t found it yet, keep looking. Don’t

settle.”

Motivation

Integrated Circuit

Small Scale Integrated(SSI) 1-

10 Medium Scale Integrated(MSI)

10-100 Large Scale Integrated(LSI)

100-100,000 Very Large Scale

Integrated(VLSI) >100,000

IC Sizes

also called "chips", are electronic

circuits where all the components (transistors, diodes, resistors and capacitors) has been manufactured in the surface of a thin substrate of semiconductor material.

All ICs (chips) are made up of logic gates

These are square pieces of silicon onto which logic gates have been deposited.

Integrated Circuit

I.C can work on low voltages. They can handle limited amount of power. They are very small in size They are cheap Complex circuitry on a chip may be used to

obtain improved performance characteristics.

Integrated Circuits (IC’s)

Example of SSI Chip – Logic Gates

Example of MSI Chip - Multiplexer

Example of VLSI Chip - CPU

process signals which

represent true or false Normally the positive supply

voltage +Vs represents true and 0V represents false.

Logic Gates

Switches in Series

If several on-off switches are

connected in series they must all be closed (on) to complete the circuit.The diagram shows a simple circuit with two switches connected in series to control a lamp.

Switch S1 AND Switch S2 must be closed to light the lamp.

Switches in Series

Switches in Parallel

If several on-off switches are

connected in parallel only one needs to be closed (on) to complete the circuit.The diagram shows a simple circuit with two switches connected in parallel to control a lamp.

Switch S1 OR Switch S2 (or both of them) must be closed to light the lamp.

Switches in Parallel

The output Q is true if input A AND input B are both true: Q = A AND B An AND gate can have two or more inputs, its output is true if all inputs are true.

AND gate

The output Q is true if input A OR input B is true (or both of them are true): Q = A OR B An OR gate can have two or more inputs, its output is true if at least one input is true.

OR gate

The output Q is true when the input A is NOT true, the output is the inverse of the input: Q = NOT A A NOT gate can only have one input. A NOT gate is also called an inverter.

NOT gate (inverter)

This is an AND gate with the output inverted, as shown by the 'o' on the output. The output is true if input A AND input B are NOT both true: Q = NOT (A AND B) A NAND gate can have two or more inputs, its output is true if NOT all inputs are true.

NAND gate (NAND = Not AND)

This is an OR gate with the output inverted, as shown by the 'o' on the output. The output Q is true if NOT inputs A OR B are true: Q = NOT (A OR B) A NOR gate can have two or more inputs, its output is true if no inputs are true.

NOR gate (NOR = Not OR)

The output Q is true if either input A is true OR input B is true, but not when both of them are true:Q = (A AND NOT B) OR (B AND NOT A) This is like an OR gate but excluding both inputs being true. The output is true if inputs A and B are DIFFERENT. EX-OR gates can only have 2 inputs.

EX-OR (EXclusive-OR) gate

This is an EX-OR gate with the output inverted, as shown by the 'o' on the output. The output Q is true if inputs A and B are the SAME (both true or both false):Q = (A AND B) OR (NOT A AND NOT B) EX-NOR gates can only have 2 inputs.

EX-NOR (EXclusive-NOR) gate

Summary for all 2-input gates

Inputs Output of each gate

 A   B  AND NAND

 OR  NOR EX-OR

EX-NOR

0 0 0 1 0 1 0 1

0 1 0 1 1 0 1 0

1 0 0 1 1 0 1 0

1 1 1 0 1 0 0 1

 is a breakdown of a logic function by listing all possible values the function can attain.

Truth Table

That’s all for today

Take care!Enjoy your weekend!

Always remember that “God loves you!”

http://www.kpsec.freeuk.com/gates.htm#and

Reference