### NOT, OR, AND Gates

• AND gate
The AND gate is an electronic circuit that gives a high output (1) only if all its inputs are high. A dot (.) is used to show the AND operation i.e. A.B. Bear in mind that this dot is sometimes omitted i.e. AB

• OR gate
The OR gate is an electronic circuit that gives a high output (1) if one or more of its inputs are high. A plus (+) is used to show the OR operation.

• NOT gate
The NOT gate is an electronic circuit that produces an inverted version of the input at its output. It is also known as an inverter. If the input variable is A, the inverted output is known as NOT A. This is also shown as A’, or A with a bar over the top, as shown at the outputs.

### Solved Example:

#### 9979-01

In Boolean algebra, (A.A̅) + A =? (SSC JE EE Paper II- Sep 2019 Evening session)

Solution:
\begin{align*} (A.A̅) + A &= 0 + A \\ &= A \end{align*}