OR Gate – Logic Gates Tutorial


An OR gate is a logic gate the place the output goes HIGH (or “1”) if any of its inputs are HIGH. So if A OR B is HIGH, the output Q additionally turns into HIGH.

OR gate truth table and symbol

The logic or Boolean expression for an OR gate is A+B = Q which implies:

If A or B is true, then Q is true

Reality Desk

OR gates can have greater than two inputs. However irrespective of what number of inputs it has, it’s going to at all times give out a HIGH or logic “1” if certainly one of its inputs is HIGH.

2-input OR Gate Reality Desk

OR gate symbol
Enter A Enter B Output Q
0 0 0
0 1 1
1 0 1
1 1 1

3-input OR Gate Reality Desk

3-input OR gate symbol
Enter A Enter B Enter C Output Q
0 0 0 0
0 0 1 1
0 1 0 1
0 1 1 1
1 0 0 1
1 0 1 1
1 1 0 1
1 1 1 1

IC Options with OR Gates

Pinout for the 4071 IC

If you wish to experiment and construct circuits with OR gates, you’ll discover them in each the 4000 IC sequence and the 7400 IC sequence:

  • 4071: 4 2-input OR gates
  • 4075: Three 3-input OR gates
  • 74HC32: 4 2-input OR gates (HC is the household, may also be LS/HCT/…)
  • 74HC4075: Three 3-input OR gates (HC is the household, may also be LS/HCT/…)

These ought to all be out there as hobbyist-friendly through-hole chips. Simply be sure to purchase the DIP bundle model.

Instance Circuit: Testing an OR gate

Beneath is an easy sensible circuit you possibly can construct to check how this gate works. A Gentle-Emitting Diode (LED) activates whenever you press both of the buttons A OR B. The circuit demonstrates the fundamental operation of an OR gate.

Simple circuit for testing an OR gate

Subsequent Step within the Logic Gates Tutorial

Take a look at the opposite articles on this logic gates tutorial:

NOT Gate/Inverter
AND Gate
NAND Gate
OR Gate – (You’re right here)
NOR Gate
XOR Gate
XNOR Gate

Again to the Logic Gates Overview





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