Logic Gates

Question 1

What are Logic Gates?

Answer 1

They are circuits used to perform logical operations

Question 2

What is a Truth Table?

Answer 2

A Truth Table is a diagram that shows all possible logical inputs and their associated outputs.

Question 3

Name the 6 logic gates.

Answer 3

AND
OR
NOT
XOR
NAND 
NOR

Question 4

what does a NOT gate do and what does it look like and how is it represented in an expression?

Answer 4

• The output is the inverse of the input
• Has a triangle and a little circle
• represented by an overbar, Q = ‾A

Question 5

what does a AND gate do and what does it look like and how is it represented in an expression?

Answer 5

• Two or more inputs where the output is true if all inputs are true
• Has a D shape
• represented by a dot, Q = A . B

Question 6

what does an OR gate do and what does it look like and how is it represented in an expression?

Answer 6

• Two or more inputs where the output is true if either or both inputs are true
• Has a crescent shape
• represented by a plus, Q = A + B

Question 7

what does an XOR gate do and what does it look like and how is it represented in an expression?

Answer 7

• Takes two or more inputs where the output is true if one input is exclusively true
• Has a crescent shape with an extra curved line
• represented by a circle with a plus inside, Q = A⊕B

Question 8

what does a NAND gate do and what does it look like and how is it represented in an expression?

Answer 8

• It inverts the output of an AND gate
• Has a D shape and a little circle
• represented by an overbar over A . B

Question 9

what does a NOR gate do and what does it look like and how is it represented in an expression?

Answer 9

• Takes two or more inputs where the output is true when all inputs are false
• Has a crescent shape with a little circle
• represented by an overbar over A + B

Question 10

How do you know how many rows to fill in in a logic table?

Answer 10

Do 2 to the power of the number of inputs
2^2 inputs = 4 rows
2^3 inputs = 8 rows