Hazard-free SOP circuit: build and simulate it online

F = A·B̄ + B·C glitches when B changes with A = C = 1; the consensus term A·C covers the gap.

Build the hazard-free sop in the free online simulator — it checks your circuit automatically.

What you need

  • 3 logic switches labelled A, B, C
  • 1 probes labelled F
  • 2 AND gates
  • 1 NOT gate
  • 3 AND gates

Step by step

  1. Inputs and output. From the Logic section of the library, drop digital inputs (0/1 boxes) or logic switches for the inputs, and digital outputs or probes for the outputs; give each its label in the inspector (the checker finds them by label). Switches A, B, C; Probe F
  2. The two product terms. A·B̄ needs a NOT on B; B·C is an AND.
  3. Add the consensus term. A·C is redundant for the truth table, but it holds F at 1 while B switches — no static-1 hazard. A third AND (A·C), a 3-input OR
  4. Prove it. The function must still be right in all 8 rows.

Truth table

ABCF
0000
0010
0100
0111
1001
1011
1100
1111

Frequently asked questions

How do you build a hazard-free sop?

F = A·B̄ + B·C glitches when B changes with A = C = 1; the consensus term A·C covers the gap. In short: inputs and output, then the two product terms, then add the consensus term, then prove it.

What is the truth table of a hazard-free sop?

It has 3 inputs (A, B, C) and 1 output (F), so 8 rows. The full table is on this page; the Embedded Lab checks all of them against your circuit.

What parts do you need for a hazard-free sop?

2 AND gates; 1 NOT gate; 3 AND gates — plus logic switches for the inputs and probes for the outputs.

Can I simulate a hazard-free sop online for free?

Yes. Open it in the BitForBytes Embedded Lab, a free browser-based circuit and logic simulator: drag in the gates, wire them, and press "Check my circuit" — every input combination is simulated and marked for you. No download or sign-up needed.

Part of DSD 42 · Hazards in the free BitForBytes digital system design course.

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