Logic Gates

Logic Gates
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ComputingLower Secondary (Key Stage 3)

This lesson contains 29 slides, with interactive quizzes and text slides.

time-iconLesson duration is: 50 min

Items in this lesson

Logic Gates

Slide 1 - Slide

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 an understanding of Boolean logic and Algebra

Slide 2 - Slide

Starter

Slide 3 - Slide

Slide 4 - Slide

What could you see in the previous slide?

Slide 5 - Open question

Main Activity

Slide 6 - Slide

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.

Slide 7 - Slide

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.

Slide 8 - Slide

What are the different Logic Gates?


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

Slide 9 - Slide

The most common logic gates are:

AND Gate

NOT Gate 

OR Gate

Slide 10 - Slide

Slide 11 - Slide

AND Gate - Diagram and Truth Table
Output is true if: All inputs are true

Slide 12 - Slide

NOT Gate - Diagram and Truth Table
Output is true if:​ Input is false​
Output is false if:​ Input is true

Slide 13 - Slide

OR Gate-Diagram and Truth Table
Output is true if:​  At least one Inputs is true

Slide 14 - Slide

Let's have a go at creating these...
Click on this link

I want you to create the AND, NOT, OR Gates.

Slide 15 - Slide

More than one input...
AND Gate 

Slide 16 - Slide

More than one input
OR Gate

Slide 17 - Slide

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. This is also in your worksheet

Slide 18 - Slide

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

Slide 19 - Slide

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.

Slide 20 - Slide

Boolean Algebra
What is 'Boolean Algebra'?

The text that describes the way the gates are connected.

Slide 21 - Slide

Y = A AND NOT B

Slide 22 - Slide

Y = NOT(A AND B)

Slide 23 - Slide

Y = (A AND B) OR C

Slide 24 - Slide

What would be the expression for this?

Slide 25 - Open question

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.

Slide 26 - Slide

Plenary

Slide 27 - Slide

OR
NOT
AND

Slide 28 - Drag question

What is the correct expression for the OR Gate
A
Y = A OR B
B
Y = A OR C
C
A OR B = Y
D
Y = A - B

Slide 29 - Quiz