3-Input NOR Gate

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Description

This MicroSim provides an interactive demonstration of a 3-input NOR gate. The simulation displays the standard NOR gate symbol (OR shape with an inversion bubble at the output), three clickable input toggles, and a complete eight-row truth table.

The 3-input NOR gate outputs 1 only when all three inputs are 0. For every other input combination, the output is 0. This is the complement of the 3-input OR gate. As you toggle inputs, the truth table highlights the current row in real time.

Key Features

  • ● Standard NOR gate symbol with inversion bubble and three input wires
  • ● Three clickable toggle buttons for inputs A, B, and C
  • ● Eight-row truth table with real-time row highlighting
  • ● Live output display showing the Boolean expression NOT(A OR B OR C) = Y

How to Use

  1. Click the toggle button next to input A to switch it between 0 and 1
  2. Click the toggle button next to input B to switch it between 0 and 1
  3. Click the toggle button next to input C to switch it between 0 and 1
  4. Observe the gate output update in real time
  5. Watch the truth table highlight the row matching the current input combination
  6. Verify that the output is 1 only when all three inputs are 0

Learning Objectives

Bloom Level: Understand (L2)

After using this MicroSim, students will be able to:

  • ✓ Extend the 2-input NOR gate concept to three or more inputs
  • ✓ Predict the output of a 3-input NOR gate for any input combination
  • ✓ Explain the relationship between NOR and OR gates (NOR = NOT OR)
  • ✓ Recognize that NOR is a universal gate capable of implementing any Boolean function

Lesson Plan

Before the Simulation (5 minutes)

  • ● Review the 2-input NOR gate and its truth table
  • ● Remind students that NOR is the complement of OR
  • ● Introduce NOR as a universal gate alongside NAND

During the Simulation (15 minutes)

  1. Start with all inputs at 0 and verify the output is 1
  2. Toggle input A to 1 and observe the output drops to 0
  3. Return A to 0 and toggle B to 1 to see the same effect
  4. Explore all eight combinations systematically
  5. Find the single combination that produces output 1 (A=0, B=0, C=0)
  6. Compare with the OR truth table to confirm NOR is the complement of OR

After the Simulation (5 minutes)

  • ● Discuss why NOR gates are universal (can implement any Boolean function)
  • ● Show that NOR-only logic is common in certain IC families
  • ● Connect to De Morgan's theorem: NOT(A OR B OR C) = NOT A AND NOT B AND NOT C

References