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# what is a logic gate? draw the symbol and give the truth table for not gate. why not gate is called inverter?

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## What is a logic gate? Draw the symbol and give the truth table for NOT gate. Why NOT the gate is called an inverter?

What is a logic gate? Draw the symbol and give the truth table for NOT gate. Why NOT the gate is called an inverter?

What is a logic gate? Draw the symbol and give the truth table for NOT gate. Why NOT the gate is called an inverter?

### SOLUTION

Logic gate: A digital circuit with one or more input signals but only one output signal is called a logic gate. It is a switching circuit that follows a certain logical relationship between the input and output voltages.Schematic symbol:

NOT gate symbol

The truth table for NOT gate:Input Output

X Y 0 1 1 0

Reason:

NOT gate has one input and one output.

It produces a ‘high’ output or output ‘1’ if the input is ‘0’. When the input is ‘high’ or ‘1’, its output is ‘low’ or ‘0’.

That is, it produces a negated version of the input at its output.

Hence, NOT gate is called an inverter.

Concept: Logic Gates

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Chapter 16: Semiconductors Devices - Short Answer II

Q 5 Q 4 Q 6

### APPEARS IN

SCERT Maharashtra Question Bank 12th HSC 2022 Physics (Science) by Maharashtra State Board

Chapter 16 Semiconductors Devices

Short Answer II | Q 5

स्रोत : www.shaalaa.com

## Logic NOT Gate Tutorial with Logic NOT Gate Truth Table

Digital Electronics Tutorial about the Logic NOT Gate also called an Inverter and the Logic NOT Gate Truth Table used in TTL and CMOS Logic Gate circuits

## Logic NOT Gate Tutorial

The Logic NOT Gate is the most basic of all the logical gates and is often referred to as an Inverting Buffer or simply an Inverter

Inverting NOT gates are single input devicse which have an output level that is normally at logic level “1” and goes “LOW” to a logic level “0” when its single input is at logic level “1”, in other words it “inverts” (complements) its input signal. The output from a NOT gate only returns “HIGH” again when its input is at logic level “0” giving us the Boolean expression of:  A = Q.

Then we can define the operation of a single input digital logic NOT gate as being:

“If A is NOT true, then Q is true”

## Transistor NOT Gate

A simple 2-input logic NOT gate can be constructed using a RTL Resistor-transistor switches as shown below with the input connected directly to the transistor base. The transistor must be saturated “ON” for an inverted output “OFF” at Q.

Logic NOT Gates are available using digital circuits to produce the desired logical function. The standard NOT gate is given a symbol whose shape is of a triangle pointing to the right with a circle at its end. This circle is known as an “inversion bubble” and is used in NOT, NAND and NOR symbols at their output to represent the logical operation of the NOT function. This bubble denotes a signal inversion (complementation) of the signal and can be present on either or both the output and/or the input terminals.

## The Logic NOT Gate Truth Table

Symbol Truth Table

Inverter or NOT Gate

A Q 0 1 1 0

Boolean Expression Q = not A or A Read as inverse of A gives Q

Logic NOT gates provide the complement of their input signal and are so called because when their input signal is “HIGH” their output state will NOT be “HIGH”. Likewise, when their input signal is “LOW” their output state will NOT be “LOW”. As they are single input devices, logic NOT gates are not normally classed as “decision” making devices or even as a gate, such as the AND or OR gates which have two or more logic inputs. Commercial available NOT gates IC’s are available in either 4 or 6 individual gates within a single IC package.

The “bubble” (o) present at the end of the NOT gate symbol above denotes a signal inversion (complementation) of the output signal. But this bubble can also be present at the gates input to indicate an active-LOW input. This inversion of the input signal is not restricted to the NOT gate only but can be used on any digital circuit or gate as shown with the operation of inversion being exactly the same whether on the input or output terminal. The easiest way is to think of the bubble as simply an inverter.

### Signal Inversion using Active-low input Bubble

Bubble Notation for Input Inversion

### NAND and NOR Gate Equivalents

An Inverter or logic NOT gate can also be made using standard NAND and NOR gates by connecting together ALL their inputs to a common input signal for example.

A very simple inverter can also be made using just a single stage transistor switching circuit as shown.

When the transistors base input at “A” is high, the transistor conducts and collector current flows producing a voltage drop across the resistor R thereby connecting the output point at “Q” to ground thus resulting in a zero voltage output at “Q“.

Likewise, when the transistors base input at “A” is low (0v), the transistor now switches “OFF” and no collector current flows through the resistor resulting in an output voltage at “Q” high at a value near to +Vcc.

Then, with an input voltage at “A” HIGH, the output at “Q” will be LOW and an input voltage at “A” LOW the resulting output voltage at “Q” is HIGH producing the complement or inversion of the input signal.

## Hex Schmitt Inverters

A standard Inverter or Logic NOT Gate, is usually made up from transistor switching circuits that do not switch from one state to the next instantly, there will always be some delay in the switching action.

Also as a transistor is a basic current amplifier, it can also operate in a linear mode and any small variation to its input level will cause a variation to its output level or may even switch “ON” and “OFF” several times if there is any noise present in the circuit. One way to overcome these problems is to use a Schmitt Inverter or Hex Inverter.

We know from the previous pages that all digital gates use only two logic voltage states and that these are generally referred to as Logic “1” and Logic “0” any TTL voltage input between 2.0v and 5v is recognised as a logic “1” and any voltage input below 0.8v is recognised as a logic “0” respectively.

स्रोत : www.electronics-tutorials.ws

## What is a NOT Gate?

The NOT gate is a single input single output gate, also known as Inverter as it converts 0 into 1 or I into 0. The switching circuit & truth table is shown.

## NOT Gate

The NOT gate is a single input single output gate. This gate is also known as Inverter because it performs the inversion of the applied binary signal, i.e., it converts 0 into 1 or 1 into 0.

In other words, the gate which has a high input signal only when their input signal is low such type of gate is known as the not gate. The logic symbol for the gate is shown below:

The symbol of the not gate is a triangle with a bubble on its end. This bubble is known as the inversion bubble. It gives the complement of the input signal. It is also known as decision-making devices because it has only one input. The switching circuit diagram of the NOT gate is shown below:

The switching circuit illustrates that the lamp will glow when switch A is open and will go off when the switch A is closed.

The truth table of the gate is given below:

A Z 0 1 1 0

This is all about NOT gate.

### Related terms:

OR Gate

Exclusive NOR Gate – EXNOR Gate

AND Gate

Exclusive OR Gate – EXOR Gate

NOR Gate

स्रोत : circuitglobe.com

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Mohammed 9 month ago

Guys, does anyone know the answer?