Table of Contents

## Digital Electronics

In simple language, the branch of electronics that deals with digital circuits are called digital electronics.

- A continuously varying signal voltage or current is called an
**analog signal.**

For example, a sinusoidal voltage.

- In an analog electronic circuit, the output voltage changes continuously according to the input voltage variations…the output voltage can have an infinite number of values.

- A signal voltage or current which can have only two discrete values is called a
**digital signal.**

For example, a square wave

- An electronic circuit that is designed for two-state operation is called a
**digital circuit.**

These days digital circuits are being used in many electronic products such as video games, microwave ovens, oscilloscopes, etc.

**Advantages of digital electronics**

**1.** Digital systems can be normally easily designed.

**2.** Digital circuits are less affected by noise.

**3. **Storage of information is easy with a digital circuit.

**4. **Digital circuits provide greater accuracy and precision.

**5.** More digital circuitry can be fabricated on integrated chips.

**The disadvantage of digital electronics**

- The digital circuits can handle only digital signals, it requires encoders and decoders, due to which the cost of the equipment is increased.

**2**. Under certain situations the use of only analog techniques is simpler and more economical than the process of signal amplification.

**3**. However since the advantages the disadvantages therefore we are switching to digital techniques at a faster pace.

**Digital Circuit**

An electronic circuit that handles only a digital signal is called a digital circuit.

or

An electronic circuit in which a state switches between the two-state with time or with the change of the input states, and it is its state at the inputs and the outputs which have significance is called a digital circuit.

**Advantages of digital circuit**

**1.** Noise free as output is measured in terms of its state, not in terms of voltage, current, or frequency, a state has a definiteness.

**2.** Capabilities of logical decision, arithmetic, and Boolean operation on the binary number.

**Disadvantage**

**1. **Slower speed due to a greater number of components to represent a state.

**2.** The circuit has complexities also. To represent a big decimal number a large number of components is needed.

**Digital coding**

In a digital circuit, each piece of information is defined by an equivalent combination of binary digits. A complete group of these combinations which represent numbers, letters,s or symbols is called digital coding.

The group of Os and 1s in the binary number can be thought of as a code representing the decimal numbers. When a decimal number is represented by its equivalent binary number, it is called straight binary coding.

**Types of code**

**1. BCD code **

- It is also known as natural BCD and is very convenient for representing decimal digits in a digital circuit.
- It consists of four bits from 0000 to 1001 representing the decimal numbers from 0 to 9.1010 to 1111 are don’t care about conditions since they do not any meaning in BCD.

**2.Excess-3 code**

- The code can be derived from BCD by adding 3 to each coded number. It is useful when it is desired to obtain the 9’s complement of a decimal represented by this code. The 9’s complement is obtained simply by complementing each bit.
- This code can be conveniently used for performing subtracting operations on digital computers.

**3. Gray code.**

- In this code only a bit changes between any two successive numbers.
- It is mainly used in the location of angular positions of a rotating shaft.

**4. Octal code**

- The octal system is an 8-base system.
- It bases 3 bits to represent one octal digit.

**5. Hexadecimal code**

- The hexadecimal system is a base 16 system.
- It uses four bits to represent 0 to 9 continued by alphabetical characters from A to F.

**Logic Gates**

A digital circuit with one or more input signals but only one output signal is called a logic gate. Or

A logic gate is an electronic circuit that makes logical decisions.

#### Types of logic gate

1. NOT Gate 2.NAND Gate

3. AND Gate 4. OR Gate

5. NOR Gate 6.XOR Gate