Basic logic gates

Basic logic gates

A logic gate is a physical device implementing a Boolean function. Logics gates instant decisions depending on the inputs. There are three types of logics AND, OR & NOT and can be expressed in Algebraic form

Now, most of the Logic gates are implemented using MOSFETs (metal–oxide–semiconductor field-effect transistors). But can also be constructed using vacuum tubes, electromagnetic relays (relay logic), fluidic logic, pneumatic logic, optics, molecules, or even mechanical elements.

AND Logic Gate

  • AND logic gate is similar to an arithmetic multiplication operation, It performs the following operations
  • Produces a logic HIGH output when both the inputs are HIGH
  • Produces a logic LOW output when any one input or both the input are LOW

Truth Table

XYX AND Y
000
010
100
111

Logic diagram

OR Logic Gate

  • OR gate acts as a selector and it always selects the highest possible output from input
  • Produces an logic high output when any one input is high
  • Produces an logic low output when both the inputs are low

Truth Table

XYX OR Y
000
011
101
111

Logic diagram

NOT Logic Gate

  • Produces a complement output for the given input
  • produces a 0 when input is 1 and produces an output 1 when input is 0

Truth Table

XNOT A
01
10

Logic diagram

NOR Logic Gate

  • NOR is a universal gate
  • Produces an logic HIGH output when both inputs are LOW
  • Produces an logic LOW output when any one input is HIGH

Truth table and logic diagram

NAND Logic Gate

  • NAND is a universal gate
  • Produces an logic HIGH output when any one input is LOW
  • Produces an logic LOW output when both the inputs are at logic HIGH

XOR Logic Gate

 The output is HIGH if either input X or input Y is HIGH exclusively   LOW when both are the same.

TRUTH TABLE

Input 1Input 2Output
XYZ
000
011
101
110

Logic diagram

XNOR Logic Gate

  • If both input X and Y are same then the output is high
  • LOW when both are different

Truth Table

XY𝒐𝒖𝒕 = 𝑥 ⨀  𝑦
001
010
100
111

Logic diagram

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