2-to-4 decoder: build and simulate it online
Two inputs select exactly one of four outputs.
Build the 2-to-4 decoder in the free online simulator — it checks your circuit automatically.
What you need
- 2 logic switches labelled A, B
- 4 probes labelled D0, D1, D2, D3
- a decoder (block or gates)
Step by step
- Inputs and outputs. 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 (MSB), B; Probes D0, D1, D2, D3
- Decode. The Decoder block, or four ANDs: D0 = ĀB̄, D1 = ĀB, D2 = AB̄, D3 = AB.
- Prove it. All four codes. One-hot: exactly one D is 1
Truth table
| A | B | D0 | D1 | D2 | D3 |
|---|---|---|---|---|---|
| 0 | 0 | 1 | 0 | 0 | 0 |
| 0 | 1 | 0 | 1 | 0 | 0 |
| 1 | 0 | 0 | 0 | 1 | 0 |
| 1 | 1 | 0 | 0 | 0 | 1 |
Frequently asked questions
How do you build a 2-to-4 decoder?
Two inputs select exactly one of four outputs. In short: inputs and outputs, then decode, then prove it.
What is the truth table of a 2-to-4 decoder?
It has 2 inputs (A, B) and 4 outputs (D0, D1, D2, D3), so 4 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 2-to-4 decoder?
a decoder (block or gates) — plus logic switches for the inputs and probes for the outputs.
Can I simulate a 2-to-4 decoder 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 23 · Decoders in the free BitForBytes digital system design course.