Understanding Basic Logic Gates and Types

By | October 7, 2021

Understanding Basic Logic Gates and their Types

Logic gates are the basis for forming a digital electronics system that functions to convert one or more inputs into a logical output signal. Logic gates operate based on the binary number system that only have 2 symbol codes,  0 and 1 using Boolean Algebra Theory.

Logic Gates which are applied in Digital Electronics Systems basically use Electronic Components such as Integrated Circuits (IC), Diodes, Transistors, Relays, Optical and Mechanical Elements.

Types of Basic Logic Gates and Symbols

There are 7 types of Basic Logic Gates that make up a Digital Electronics System :

1. AND Gate
2. OR Gerbang Gate
3. NOT Gerbang Gate
4. NAND Gate
5. NOR Gerbang Gate
6. X-OR (Exclusive OR) Gate
7. X-NOR (Exclusive NOR) Gate

A table containing combinations of Input Variables that produces a Logical Output is called a “Truth Table”

Logic Truth table

 

Input and Output on a Logic Gate only has 2 levels. The two levels can generally be represented by:

    • HIGH (high) and LOW (low)
    • TRUE (true) and FALSE (false)
    • ON (On) and OFF (Off)
    • 1 and 0

Example of its application to an electronic circuit that uses TTL transistors (transistor logic), then 0V in the circuit will be assumed as “LOW” or “0” while 5V will be assumed as “HIGH” or “1”.

The following is a brief explanation of the 7 types of Basic Logic Gates along with their Symbols and Truth Tables.

AND Gate

AND gate requires 2 or more Inputs (Inputs) to produce only 1 Output (Output). The AND gate will produce a Logic 1 Output if all inputs are Logic 1 and will produce a Logic 0 Output if one of the inputs is Logic 0. The symbol that indicates the AND Gate Operation is a dot. (“.”) or use no sign at all. For example: Z = X.Y or Z = XY.

AND Gate Symbol and Truth Table

AND Gate

AND Truth Table

OR Gate

OR Gate requires 2 or more Inputs (Inputs) to produce only 1 Output (Output). The OR gate will produce an Output (Output) 1 if one of the Inputs (Input) has a value of Logic 1 and if you want to produce an Output (Output) Logic 0, then all Inputs (Inputs) must have a value of Logic 0.

The symbol indicating the Logical OR Operation is the Plus sign (“+”). For example: Z = X + Y.

OR Gate Symbol and Truth Table

OR Gate

OR Truth Table

 

NOT Gate

A NOT gate only requires an Input (Input) to produce only 1 Output (Output). NOT gate is also called an inverter because it produces an output that is opposite (opposite) to the input or input. This means that if we want to get an output with a logic value of 0 then the input or input must be a logic 1. NOT gate is usually denoted by a minus symbol (“-“) above the input variable.

NOT Gate Symbol and Truth Table

NOT Gate

NOT truth Table

 

NAND Gate

The meaning of NAND is NOT AND or NOT AND, NAND gate is a combination of AND gate and NOT gate which produces the opposite of AND gate output. The NAND gate will produce a Logic 0 Output if all Inputs are at Logic 1 and if there is an Input that has a value of Logic 0 it will produce a Logic 1 Output.

NAND Gate Symbols and Truth Tables

NAND Gate

NAND Truth Table

NOR Gate

The meaning of NOR is NOT OR or NOT OR, the NOR Gate is a combination of the OR Gate and the NOT Gate which produces the opposite of the OR Gate Output. The NOR Gate will produce a Logic Output of 0 if any of the Inputs (Inputs) is logical 1 and if you want to get a logic 1 output, then all inputs must have a logic 0 value.

NOR Gate Symbols and Truth Tables (NOR Gate)

NOR Gate

NOR Truth Table

X-OR Gate

X-OR stands for Exclusive OR which consists of 2 Inputs (Inputs) and 1 Logic Output (Output). The X-OR gate will produce a Logic 1 Output if all of its Inputs have different Logic values. If the Input Logic values ​​are the same, it will give a Logic Output result of 0.

X-OR Gate Symbols and Truth Tables

X-OR Gate

X-OR Truth Table

X-NOR Gate

The X-NOR Gate also consists of 2 Inputs and 1 Output. X-NOR stands for Exclusive NOR and is a combination of an X-OR Gate and a NOT Gate. The X-NOR gate will produce a Logic 1 Output if all inputs or inputs have the same logic value and will produce a logic 0 output if all inputs or inputs have different logic values.

This is the opposite of the X-OR (Exclusive OR) Gate.

X-NOR Gate

X-NOR Truth Table