Logic Circuits

Courses GCSE Computer Science Logic Gates Logic Circuits

Combing Logic gates into logic circuits

By connecting different logic gates together in various configurations, you can create more complex logic functions and circuits.

Two invaluable uses of logic circuits include:

Half / Full Adders - some that machines can perform arithmetic
Flip-flop circuits - some that machines can store data in electronics

For the examination you will need to be able to:

Draw logic gates and circuits
Complete truth tables for logic circuits

When evaluating a logic circuit you always work from left to right.

(NOT A) AND B

Here in the example the output of the NOT gate feeds in as an input into the AND gate.

Truth Table

A	B	not A	(not A) and B
0	0	1	0
0	1	1	1
1	0	0	0
1	1	0	0

Demo

(A AND B) OR C

The expression "(A AND B) OR C" represents a logical operation that involves three variables, A, B, and C, along with the AND (AND) and OR (OR) logical operators.

Truth Table

A	B	C	A AND B	(A AND B) OR C
0	0	0	0	0
0	0	1	0	1
0	1	0	0	0
0	1	1	0	1
1	0	0	0	0
1	0	1	0	1
1	1	0	1	1
1	1	1	1	1

Demo

Question

Drag gates to canvas:

Input

AND

XOR

NAND

NOR

NOT

Output

Drag gates from the palette above and connect them by dragging from output ports (right side) to input ports (left side). You can branch one output to multiple inputs by connecting from the same output port multiple times.

{"text": "Create a circuit that outputs true when at least one of the inputs A, B, or C is true.", "inputs": ["A", "B", "C"], "booleanSolution": "(A) OR (B) OR (C)"}

Question

Drag gates to canvas:

Input

AND

XOR

NAND

NOR

NOT

Output

{"text": "Design a circuit that outputs true when input A is true, input B is true, and input C is false.", "inputs": ["A", "B", "C"], "booleanSolution": "(A) AND (B) AND (NOT C)"}

Question

Drag gates to canvas:

Input

AND

XOR

NAND

NOR

NOT

Output

{"text": "Construct a circuit that outputs true when either input A or input B is true, but not both.", "inputs": ["A", "B"], "booleanSolution": "(A XOR B)"}

Question

Drag gates to canvas:

Input

AND

XOR

NAND

NOR

NOT

Output

{"text": "Design a circuit that outputs true only when input A is true and input B is false.", "inputs": ["A", "B"], "booleanSolution": "(A) AND (NOT B)"}