A NOT gate, or inverter, has one input and one output and flips the value it is given. A high input produces a low output and a low input produces a high output.

Why is the NOT gate important?

AND and OR alone can never produce an output that fires when an input is off. NOT breaks that limit, and a loop of two inverters gives a circuit two stable states — the basis of every latch, flip-flop and memory cell.

How do you build a NOT gate in Minecraft redstone?

A redstone torch on the side of a block is already a NOT gate. The torch is lit while the block is unpowered and goes out when the block is powered, inverting the signal in one component and one tick.

What is the difference between a NOT gate and a buffer?

A NOT gate inverts its input; a buffer passes it through unchanged. A buffer exists for timing and signal strength rather than logic, and two NOT gates in series make one.

How do you make a NOT gate from a NAND gate?

Tie both NAND inputs to the same signal. A NAND with equal inputs outputs the opposite of that signal, so it acts as an inverter. The same trick works with a NOR gate.

NOT gate

One input, one output, and a permanent disagreement between them. A plain-English guide to logic gates from TorchAnvil.

A NOT gate — also called an inverter — has one input and one output. It flips whatever it's given. High becomes low, low becomes high. That's the whole rule, and it is the most important gate on this page.

How to read it

A	Ā
0	1
1	0

Two rows, because one input has only two possible states. The bar over the A means "not A"; you'll also see ¬A, !A, or A' depending on whose textbook you're holding. They all mean the same thing.

Why it matters

Inversion sounds trivial and is anything but. Without it, whole families of behaviour are simply unreachable.

Consider: AND and OR can only ever turn more things on as their inputs turn on. Feed them all zeros and you get zero out. There is no way to build a circuit that says "fire when this is off" from AND and OR alone, no matter how many you chain together. NOT is the gate that breaks that ceiling.

It's also what makes memory possible. Feed a NOT's output back to its own input and you get a circuit that can never settle — it oscillates. Arrange two NOTs in a loop and you get the opposite: a circuit with two stable states that stays wherever you put it. That second arrangement is the heart of every latch and flip-flop, and therefore of every byte of RAM ever manufactured.

A worked example: the "empty" detector

Say you have a lamp that should light when a chest is empty. Your sensor gives you a signal that's high when the chest has something in it — the opposite of what you want.

You could hunt for an inverted sensor. Or you drop a NOT in the line and move on. That's the everyday use of an inverter: adapting a signal you have into the polarity you need.

Now extend it. Two chests, and you want a lamp when both are empty:

NOT(A) AND NOT(B)

Wire that up and test all four combinations. Then wire this instead:

NOT(A OR B)

Test it again. Identical results, one gate cheaper. You've just derived half of De Morgan's laws by hand — and NOT(A OR B) is exactly what a NOR gate does in a single component.

How it differs from BUFFER

A BUFFER also has one input and one output, and it does nothing to the value — high stays high. Logically it's the identity function, the gate that isn't.

A	NOT	BUFFER
0	1	0
1	0	1

So why does BUFFER exist? Because in real circuits a gate does more than compute: it restores the signal and adds delay. A buffer is a NOT that has been inverted back, used when you need the timing or the drive without the inversion. Two NOTs in series make a BUFFER, and in redstone that's literally how you build one.

In redstone

The redstone torch is a NOT gate, and this is the single most important fact in computational redstone.

Place a torch on the side of a block. Unpowered, the torch is lit and powers the dust next to it. Power that block and the torch goes out. Input on, output off — inversion, in one component, costing one redstone tick.

Every other gate in Minecraft is assembled from this behaviour. AND is three torches. NOR is one torch with two inputs on the same block. Even the humble repeater is, in effect, two inversions packed into a block with a configurable delay.

If you only remember one thing about redstone logic, remember that a torch inverts, and that everything else is built on top of that.

Building it from other gates

NOT falls out of any two-input universal gate by tying its inputs together:

NOT A = A NAND A
NOT A = A NOR A

Feed the same signal into both inputs of a NAND and it inverts. That trick is why NAND and NOR are called functionally complete: get an inverter for free and you can bootstrap every other gate from there.

Inversion in Boolean algebra

Three identities are worth memorising, because almost every simplification you'll ever do uses them.

Involution. NOT(NOT A) = A. Two inversions cancel. This is what lets you delete pairs of torches from a redstone line without changing behaviour — though never without changing timing.

Complement. A · NOT A = 0, and A + NOT A = 1. A signal AND-ed with its own inverse is always off; OR-ed with its own inverse it's always on. If a simplification ever produces one of these, you've found a branch of the circuit that can be deleted outright.

De Morgan. NOT(A · B) = NOT A + NOT B, and NOT(A + B) = NOT A · NOT B. Pushing a NOT through a bracket flips the operator.

That last one is the workhorse. It's why an AND in redstone is built as "invert both, merge, invert again", and why a NAND is one torch cheaper than an AND. The Circuit Collapsor applies these rules automatically, but doing a few by hand first makes its output far easier to read.

Gotchas

Double negation cancels. NOT(NOT A) = A, logically. But it is not free — in redstone it costs two ticks, and that delay is sometimes the entire reason for building it.
A NOT in a loop oscillates. Feed a torch's output back into its own block and you get a clock, not a value. That's a feature when you want a clock and a bug when you don't.
Inverting is not the same as swapping. NOT(A AND B) is not NOT(A) AND NOT(B). De Morgan's law says the AND becomes an OR when you push the NOT inwards: NOT(A AND B) = NOT(A) OR NOT(B). Forgetting to flip the operator is the classic Boolean-algebra slip.

Try it

The demo on the right is one lever, one NOT, one lamp. The lamp is lit when the lever is off — which looks broken until you remember what the gate does.

Then chain two NOTs and watch the lamp follow the lever again. You've built a BUFFER out of inverters.

Frequently asked questions

What is a NOT gate?: A NOT gate, or inverter, has one input and one output and flips the value it is given. A high input produces a low output and a low input produces a high output.
Why is the NOT gate important?: AND and OR alone can never produce an output that fires when an input is off. NOT breaks that limit, and a loop of two inverters gives a circuit two stable states — the basis of every latch, flip-flop and memory cell.
How do you build a NOT gate in Minecraft redstone?: A redstone torch on the side of a block is already a NOT gate. The torch is lit while the block is unpowered and goes out when the block is powered, inverting the signal in one component and one tick.
What is the difference between a NOT gate and a buffer?: A NOT gate inverts its input; a buffer passes it through unchanged. A buffer exists for timing and signal strength rather than logic, and two NOT gates in series make one.
How do you make a NOT gate from a NAND gate?: Tie both NAND inputs to the same signal. A NAND with equal inputs outputs the opposite of that signal, so it acts as an inverter. The same trick works with a NOR gate.