Logic Gates V4

• Computing
• Lower Secondary (Key Stage 3)

Logic Gates

KO: Demonstrate an understanding of logic gates and Boolean logic

All

• To be-able to recognise a logic gate.
• To be-able to understand the three different logic gates (NOT, AND, OR).

Most 

• To be-able to recognise the different logic gates and complete truth tables for them.
• To be-able to solve several gate problems. 

Some 

• To be-able to create a circuit using the different logic gates.
• To demonstrate a clear understanding of Boolean logic and Algebra.

Starter

List all of the places you might find a circuit?

Main Activity

Recap - What is a Logic Gate?

A logic gate is a device that acts as a building block for digital circuits. They perform basic logical functions that are fundamental to digital circuit.

Recap - What is a 'Truth Table'?

This is a way of representing the inputs of the gates in a table using Boolean representation – 1’s & 0’s, or true & false. Each logic diagram has its own unique truth table.

What are the different Logic Gates?

AND, OR, XOR, NOT, NAND, NOR and XNOR.

The most common logic gates are:

AND Gate

NOT Gate 

OR Gate

AND Gate - Diagram and Truth Table

Output is true if: All inputs are true

NOT Gate - Diagram and Truth Table

Output is true if:​ Input is false​

Output is false if:​ Input is true

OR Gate-Diagram and Truth Table

Output is true if:​  At least one Inputs is true

Video 

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Main Task

Logic.ly

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Worksheet 

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More than one input...

AND Gate 

Answers

More than one input

OR Gate

Answers

Multiple Gates

Gates can be connected to other gates for more complex circuits​

Below we can see an AND gate along with a NOT gate. 

Answers

Multiple Gates

Below we can see an AND gate along with a OR gate.

Answers

What we have learnt so far...

• Truth tables represent what a binary output will be based on binary inputs and the currently used logic gate​.

• AND gates will produce a binary value of 1 when all inputs are a binary value of 1​.

• OR gates will produce a binary value of 1 when at least 1 input is a binary value of 1​.

• NOT gates will produce the opposite value of the input.

Boolean Algebra

What is 'Boolean Algebra'?

The text that describes the way the gates are connected.

Y = A AND NOT B

Y = NOT(A AND B)

Y = (A AND B) OR C

What would be the expression for this?

Research Task

In your small groups you must research the remainder of the gates. I want a definition and example.

XOR, NOR, XNOR, NAND

Be prepared to share with the class.

Plenary

OR

NOT

AND

What is the correct expression for the OR Gate

1. Y = A OR B
2. Y = A OR C
3. A OR B = Y
4. Y = A - B