Name: Energy Band Gap
Uploaded: 2019-07-19
Duration: 5 min 21 s
Description: We know that certain materials conduct electricity whereas some don’t. Has it got anything to do with their energy bandgap? Let’s find out in this video.

Question

What is a NAND gate? Write its symbol, truth table, and input and output waveforms. Why it is called the universal gate.

Accepted Answer

The NAND gate or “Not AND” gate is the combination of two basic logic gates, the AND gate and the NOT gate connected in series. The NAND gate and NOR gate can be called the universal gates since the combination of these gates can be used to accomplish any of the basic operations. Hence, NAND gate and NOR gate combination can produce an inverter, an OR gate or an AND gate.

The output of a NAND gate is high when either of the inputs is high or if both the inputs are low. In other words, the output is always high and goes low only when both the inputs are high. The logic NAND function is given by the Boolean expression

$Y = A . B$

Here A, B are the inputs and Y is the output.

The Boolean expression given for a NAND gate is that of logical addition, and it is opposite to AND gate. The Boolean expression is given by a single dot (.) with an over line over the expression to show the NOT or the logical negation of the NAND gate.

The symbol of the NAND gate is represented as a combination of AND gate and NOT gate. The Boolean expression is given as

$Y = A . B$

The truth table of a NAND gate is given below

A B Y

0 0 1

0 1 1

1 0 1

1 1 0

NAND Gate is called Universal Gates because all the other gates (NOT, AND, OR and NOR)can be created by using this gate.

What is a NAND gate? Write its symbol, truth table, and input and output waveforms. Why it is called the universal gate.

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