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**LOGIC GATE (ELECTRONICS)**

The basic building block of digital circuit is a logic gate .The logic gate enter two or more input signals for designed and produced one output signals .The terminal of logic gate are two conditions 0(for low) & 1 (For high)

The basic gate are

**AND**,

**OR**, &

**NOT**gate where the complex gate are

**NAND**,

**NOR**, &

**XO**R gate &

**XNOR**gate. And

**NAND**gate and

**NOR**gate are called universal gate.

**AND gate:**

The function of

**AND**

**gate**is identical .

**AND**gates takes two or more signal and return only one signal .

**AND gate**is called logic multiplication.

truth table :

AND gate for 2-input |

The boolean expression for the 2-input gate is F = A . B

for the 3-input gates is F= A . B . C

AND gate for 2-input |

OR gate:

#### The function of OR gate is identical.OR gates takes two or more signal as input and give output only one output. OR gate is called logic addition.

Truth table:OR gate for 2-input |

The Boolean expression for the 2-input gate is F = A + B

for the 3-input gate is F= A + B + C

OR gate for 2-input |

**NOT gate:**

The function of

**NOT**

**gate**is identical to that of

**NOT**

**gate**operator. The

**NOT**

**gate**circuit inverts the logic sense of binary signals .so therefor called Inverters.

Truth table:

NOT gate for 2-input |

The Boolean expression for the 2-inputs gate is F = A'

NOT gate for 2-input |

**NAND gate:**

**This gate is combination of**

**AND**and

**NOT gates**. So it is a complex gate. The graphically combination of

**NAND gate**is

**AND gate**symbol.

Truth table:

NAND gate for 2-input |

The Boolean expression for 2-input gate is F = (A.B)'

NAND gate for 2-input |

**NOR gate:**

The gate of function is combination of the

**OR**and

**NOT gate**. The graphically symbol of

**NOR gate**symbol with bubble .

**NOR gate**is also reffered to as inverted

**OR gate.**

Truth table:

NOR gate for 2-input |

The Boolean expression for 2-inputs gate is F = (A + B)'

for 3-inputs gate is F= (A + B + C)'

NOR gate for 2-input |

**XOR gate:**

**The**

**XOR gate**stand for exclusive

**OR gate**.

**XOR**

**gate**are use for two way commonly use in our homes for staircase light .

Truth table:

XOR gate for 2-input |

The Boolean expression for 2-input gate is F = (A+B) . (A'+B')

XOR gate for 2-input |

**XNOR**

**gate:**

**Truth table:**

XNOR gate for 2-input |

The Boolean expression for 2-input

**XNOR gate**F = A . B + A' . B'

3-input XNOR gate F = A . B . C + A' . B' . C'

XNOR gate for 2 and 3 -inputs |