Question

What is the NOR gate symbol?

Answer 1

A **NOR gate** is a type of logic gate that produces an output of **1 (true)** only when **all inputs are 0 (false)**. It is the combination of a NOT gate (inverter) and an OR gate. The output of a NOR gate is the inverse of the output of an OR gate.

### NOR Gate Symbol:
The NOR gate symbol is derived from the OR gate symbol but with an additional inversion circle at the output. Here is the breakdown:

- **Basic Shape**: It has a similar shape to the OR gate, but with the curve at the output.
- **Inversion Circle**: At the output of the symbol, there is a small circle (or bubble), representing the NOT operation, indicating that the output is negated.
  
**Representation:**

1. **Inputs**: Usually, two inputs labeled \( A \) and \( B \) (or more, depending on the gate version).
2. **Output**: Denoted by the output label \( Y \), which is the negation of the OR operation of the inputs.
3. **Shape**: The two inputs enter a curved line (like the OR gate), and the line then ends with the circle representing inversion at the output.

### Truth Table:
| A | B | Y (Output) |
|---|---|------------|
| 0 | 0 | 1          |
| 0 | 1 | 0          |
| 1 | 0 | 0          |
| 1 | 1 | 0          |

### Boolean Expression:
The Boolean expression for the NOR gate is:

\[
Y = \overline{A + B}
\]

Where:
- \( + \) represents OR operation.
- \( \overline{ } \) represents NOT operation (inversion).

The NOR gate is crucial in digital logic design and can be used to create any other logic gate, which is why it’s often referred to as a "universal gate."