Logic Gates

Question 1

What are logic gates?

Answer 1

Logic gates are circuits that are used to perform a logical operation in computing and electronics.

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

What is an AND GATE?

Answer 3

Two or more inputs where the output is true if all inputs are true

Question 4

What is an NOT GATE?

Answer 4

The output is the inverse (opposite)
of the input.

Question 5

What is an OR GATE?

Answer 5

Two or more inputs where the output is true if either or both inputs are true

Question 6

What is an XOR GATE?

Answer 6

Two or more inputs where the output is true ONLY if one input is exclusively true.

Question 7

What is an NAND GATE?

Answer 7

Two or more inputs where the output is false when all inputs are true.

Question 8

What is an NOR GATE?

Answer 8

Two or more inputs where the output is true when all inputs are false.

Question 9

What is an half adder logic?

Answer 9

Half adder circuit carries out addition on two numbers (A and B) only

Question 10

What is an full adder logic?

Answer 10

• Full adder circuit carries out addition on two numbers (A and B) and a carry bit.
• A series of full adders can be used to add two binary numbers, as the carry bit is available at each stage of the calculation.

Question 11

What is an flip flop?

Answer 11

A flip flop is an electronic circuit that has two stable states and can be used as a memory device to store one bit of data

Question 12

What is an D type flip flop?

Answer 12

A D-type flip flop changes state with each clock pulse, so data is delayed by one clock pulse

Question 13

AND logic identities

Answer 13

1 . A = A
0 . A = 0
A . A = A
A .¯A=0

A . B = B . A
A . ( B . C ) = (A . B) . C
A + (B . C) = (A + B) . (A + C)
A . (A + B) = A

Question 14

OR logic identities

Answer 14

0 + A = A
1 + A = 1
A + A = A
A+¯A=1
A + B = B + A
A + (B + C ) = (A + B) +. C
A . (B + C) = (A . B) + (A . C)
A + (A . B) = A

Question 15

How is De Morgan’s law carried out?

Answer 15

A .B=¯(¯A+¯B) and A+ B=¯(¯A.¯B)

The laws are straightforward to remember as:
1. Change all AND operators to OR
2. Change all OR operators to AND
3. Change the logical state of each variable, so:
A=¯( A) and ¯A= A
4. Change the logical state of the complete expression, so:
expression=¯expression
(and vice versa)