Logic Gates and Digital Circuits Name:
Part 0: What is a Logic Gate
What is a logic gate? It is an elementary building block of a _____.
Most standard logic gates have two __________ and one ______________.
What is a truth table? A chart of a circuit's inputs and outputs is called its _______.
- A ___________ indicates off. A _______ indicates on.
- In order to help you predict the output of complex circuits, truth tables often have mid-values (see complex circuits later in the assignment) indicated by letters.
Part 1: And, Or & Not
And - If ALL inputs are on, the output is on. If even one input is off, the output is off.
Not - Reverses the input
Or - If ANY inputs are on, the output is on.
Part 3: Combining Logic Gates into Complex Circuits
- Predict the answers and fill in the truth table below
- Then build the circuit in Logic Lab and test if your prediction was correct. https://logic.ly/demo
- Mark any incorrect predictions by using the paint can to fill the cell red.
1) (NOT & AND gate)
A | B | Y | Z |
0 | 0 | ||
0 | 1 | ||
1 | 0 | ||
1 | 1 |
2) (NOT & AND & AND gate)
A | B | X | Y | Z |
0 | 0 | |||
0 | 1 | |||
1 | 0 | |||
1 | 1 |
3) (AND & AND & OR)
A | B | C | D | X | Y | Z |
0 | 0 | 0 | 0 | |||
0 | 0 | 0 | 1 | |||
0 | 0 | 1 | 0 | |||
0 | 0 | 1 | 1 | |||
0 | 1 | 0 | 0 | |||
0 | 1 | 0 | 1 | |||
etc. | That’s enough. You get the idea. | Do not continue this table past here. |
D) Draw your own and come up with a truth table (or trade it with a neighbour to complete each other’s truth table). Give your circuit:
- 2 or 3 inputs
- 2 or 3 different kinds of gates (using only AND, NOT & OR)
Circuit Drawing
How? Create something new in Logic Lab and then use the Snipping Tool to get a screenshot. (Start menu… Snipping tool)
Truth Table