1. Presentation on logic gates and
its applications

2. History of logic gates
 The first logic gates were developed
around 1837 and were of mechanical
form. For most of that century, these
gates went through much development
until Nikola Tesla developed circuit-based
logic in 1898. Furthermore, Boolean
algebra was introduced to circuit analysis
during the mid-19th century and shaped
the way people interpret this logic today

3.  There are many different types of logic in
electronics, where gates are made up of
many different devices such as diodes,
relays transistors, and most importantly,
integrated circuits (ICs).

4. Variations of logic gates
One of the biggest decisions to make when
dealing with Boolean logic is deciding
which gates to use to compare your logic
inputs. Here is a breakdown of different
types of logic gates including their output
truth tables when two Boolean inputs
exist:

5. AND Gate
The AND gate compares in a way
that the output is high only if both inputs
are high.

6.  OR Gate
 The OR gate will have a high output for
all input cases except when both inputs
are low.

7. NOT gate (inverter)
The output Q is true when the input A is NOT true,
the output is the inverse of the input: Q = NOT A
A NOT gate can only have one input. A NOT gate is
also called an inverter.

8. NAND gate (NAND
= Not AND)
 This is an AND gate with the output
inverted, as shown by the 'o' on the
output.
The output is true if input A AND input
B are NOT both
true: Q = NOT (A AND B)
A NAND gate can have two or more
inputs, its output is true if NOT all inputs
are true.

10. NOR gate (NOR = Not OR)
 This is an OR gate with the output
inverted, as shown by the 'o' on the
output.
The output Q is true if NOT inputs A
OR B are true: Q = NOT (A OR B)
A NOR gate can have two or more
inputs, its output is true if no inputs are
true.

11. EX-OR (EXclusive-OR) gate
The output Q is true if either input A is true OR input B is
true, but not when both of them are
true: Q = (A AND NOT B) OR (B AND NOT A)
This is like an OR gate but excluding both inputs being
true.
The output is true if inputs A and B are DIFFERENT.
EX-OR gates can only have 2 inputs.

12. EX-NOR (EXclusive-NOR) gate
This is an EX-OR gate with the output inverted, as shown
by the 'o' on the output.
The output Q is true if inputs A and B are the SAME (both
true or both
false): Q = (A AND B) OR (NOT A AND NOT B)
EX-NOR gates can only have 2 inputs.

14. Applications
Simple application of NAND gate
 The application discussed here is that of a door
closing system of an automobile. A car needs to
be so designed that the driver gets a visual
indication if any of the doors of the car is open
so that it helps to avoid accident and injury to
the passengers. Assuming there are two doors
(just for simplicity, it works for more doors as
well) where this system is fitted, the circuit can
be designed using a NAND gate as follows


15.  You can see from the figure that when
any of the switches is open due to the
door position, the NAND gate energies
the lamp inside the car, hence warning
the driver.
A Car Door Open Warning System
using a NAND Gate

16. This truth table gives us the behaviour of
lamp inside the car when any one the doors
are opened

17. 2) Fire Alarm system ( OR gate )

18. (3) Fire Control system
AND gate & OR gate

19. Some more examples
 Below is the logic gate for a simple house
alarm. The alarm protects the front and
back doors and six windows.
 Once the alarm is set if any of the doors
or windows are opened the alarm will
sound.