NOT gate using a NAND gate: two ways, live
A NAND gate becomes a NOT gate in two ways: tie both inputs together, Y = NAND(A, A) = NOT A, or tie one input to 1, Y = NAND(A, 1) = NOT A. The live circuit below builds both side by side.
NAND outputs 0 only when both inputs are 1. With both inputs joined to A, that happens exactly when A = 1, so the output is NOT A; with one input held at 1, the gate again outputs 0 only when A = 1. Both work, and they differ only electrically: tying the inputs together doubles the load on the signal driving A, while tying one to the supply leaves A driving a single input. The inverter is the first step in building every other gate from NAND, as in the AND gate from two NANDs and the OR gate from three NANDs. In CMOS a dedicated inverter is cheaper still, two transistors instead of four: see the CMOS inverter.
Open this circuit in the lab →
What you need
- 1× NAND: Y1 = NAND(A, A): both inputs tied to A
- 1× NAND: Y2 = NAND(A, 1): one input tied to the supply
Step by step
- Place an input
Aand probesY1andY2. - Wire A to both inputs of the first NAND gate and probe its output as Y1.
- Wire A to one input of the second NAND gate and the supply (1) to the other, and probe it as Y2.
- Toggle A: both outputs are always the opposite of A.
NOT from NAND truth table
| A | Y1 = NAND(A, A) | Y2 = NAND(A, 1) |
|---|---|---|
| 0 | 1 | 1 |
| 1 | 0 | 0 |
All input rows are checked on the live circuit before the page is built. The NOR version ties its spare input to 0 instead of 1: NOT gate using a NOR gate.
You can also read the full theory in the lesson on the NAND gate. Prefer to build it yourself from scratch? Open the digiwleea lab and place the gates on the canvas, or start from the logic gate simulator.
More builds: Universal gates: NAND only, NOR only
All 246 build guides, by topic
Each of these is one step from a transistor to a working CPU. Build every gate from CMOS transistors and work all the way up in the free digiwleea lab, with the free theory reference alongside.
Open the NOT gate from a NAND gate in the lab →Frequently asked
How do you make a NOT gate using a NAND gate?
Connect both inputs of the NAND gate to the signal, or connect one input to the signal and the other to logic 1. Either way the output is the inverse of the input.
How many NAND gates make a NOT gate?
One. A single NAND gate with its inputs tied together, or with one input held at 1, is an inverter.
How do you make a NOT gate from a NOR gate?
Tie both inputs of the NOR gate together, or tie one input to 0. NOR(A, A) = NOR(A, 0) = NOT A.