NOT gate truth table
The NOT gate inverts its input: the output is 1 when the input is 0, and 0 when the input is 1. Here is its full truth table, the boolean expression, and how it is actually built.
| A | Y |
|---|---|
| 0 | 1 |
| 1 | 0 |
Boolean expression: Y = A̅. A 1 in the table means a high voltage (logic true) and a 0 means low (false). Read each row as: for these inputs, the output Y is this value.
What the NOT gate does
The NOT gate (also called an inverter) is the simplest gate of all: one input, one output. In CMOS it is a single transistor pair, one PMOS pulling the output up to 1 and one NMOS pulling it down to 0, so exactly one is ever conducting.
Build it yourself
Reading a table is one thing; watching the signals flow is another. Open the logic gate simulator and wire a NOT gate up from transistors, or read the full lesson on how this gate is designed. You can also generate the table for any expression with the truth table generator.
Other gates:
The NOT gate is one small step toward a working CPU. Build every gate from CMOS transistors and work up to an 8-bit processor in the free digiwleea lab and course.
Open the gate simulator →Frequently asked
What is the truth table of a NOT gate?
The NOT gate inverts its input: the output is 1 when the input is 0, and 0 when the input is 1. With A=0 the output is 1, and with A=1 it is 0.
What is the boolean expression for NOT?
The NOT gate is written Y = NOT A (symbolically Y = A).
How many transistors does a NOT gate take?
A standard CMOS NOT gate uses about 2 transistors. In digiwleea you build it from those transistors and the simulator verifies it against this exact truth table.