Digital Electronics

A study of electronic circuits

What is Digital Electronics?

Digital electronics, digital circuits, and digital technology are electronics that are operated on digital signals. Digital techniques are much easier for getting the electronic device. These devices are used to switch into one of the known states apart from reproducing a continuous range of values. Digital circuits are made from a large collection of logic gates and a simple electronic representation of the Boolean logic function.

Now comes the term digital. The digital word comes from the same source as the word digit. Digit means something countable. Digital means the thing which deals with numbers. Now if we combine the terms digital and electronic the birth of a new term comes which is digital electronics. So in simple language the term digital electronic means controlling the flow of the electrons using some number logic.

Components of Digital Electronics

Digital electronics or the digital circuit comprises various components that perform specific functions. These components are divided into two categories:

• Active components
• Passive components

The active components are the transistors and diodes, while the passive components are the capacitors, resistors, inductors, etc.

Diodes

Diodes are manufactured using semiconductor materials. They are used for allowing the flow of current in a particular direction. Different types of diodes are used in the construction of the digital circuit.

Transistors

A semiconductor device with three terminals is known as a transistor. The main function of the transistor is to amplify the signal, and it is also used as a switching device.

Capacitors and Inductors

The main function of the capacitor is to store electrical energy. A capacitor is made using two conducting plates, and between these plates, an insulator is placed. The change in the current is resisted with the help of an inductor. They are used for storing electric energy in the magnetic field.

Logic Gates

Logic gates are the basic components of the digital circuit with one output and more than one input. AND, OR, and NOT gates are the basic gates, while NAND and NOR are the universal gates. EX-OR and EX-NOR are special gates.

Battery and Switch

The conversion of chemical energy into electric energy takes place because of the battery. It is used as a source of energy. The flow of the electric current is controlled by using a switch.

Resistors

The flow of current in the circuit is opposed by the resistor. The fixed resistor and variable resistor are the two types of resistors. All the resistors work based on Ohm’s law.

Types of Digital Circuits

• Combinational Digital Circuits
• Sequential Digital Circuits

Combinational Logic Circuit

Combinational circuits are designed using various logic gates. The implementation of combinational logic circuits is made in such a way that is output depends upon the present inputs only and it is not affected by the past history of the circuit operations.

Types of Combinational Logic Circuits:

• Circuits to perform Arithmetic and Logical operations − Adder, Subtractor, Comparators, Programmable Logic Devices etc.
• Code Converters − BCD, Binary, 7-Segment Display
• Data Transmission − Encoder, Decoder, Multiplexer, Demultiplexer

Sequential Logic Circuits

Sequential circuits consist of combinational circuits and a memory element. Sequential circuits are designed in a way that their output depends upon both the present and past inputs. The memory element is used to store the past history of the circuit operations.

Types of Sequential Logic Circuits:

• Asynchronous Sequential Circuits − Do not use clock signals, instead, the circuit is driven by the pulses of the input signal.
• Synchronous Sequential Circuits − A digital circuit in which the change in the state of the memory element is synchronised by the clock signal.

Examples of sequential circuits − Latches, Flip-Flops, Counters, Registers, etc.

How it Works?

In the world of digital electronics, controlling the flow of electrons means nothing but either allowing them to pass or not. This is similar to the switch. If the switch is ON then the current which is the flow of electrons will pass and if the switch is OFF then the current will not pass. In digital electronics, the ON state of the switch is termed as ‘1’ and the OFF state of the switch is termed as ‘0’. Also sometimes in digital electronics the term ‘1’ is referred to as TRUE logic and ‘0’ as ‘FALSE’ logic. This is shown in the figure below.

It is now clear that digital electronics deals with only two discrete values either high or ‘1’ or low ‘0’.So that sometimes this digital electronic system is called a discrete value discrete-time system. And by using this 1 or 0 logic many number systems are developed such as binary, octal, decimal, hexadecimal etc. This number of systems is used to control various operations of the system and the term digital electronics arises.

Advantages of Digital Electronics

1. Noise Reduction: The term noise means any unwanted signal which is in the information signal and which distorts the original information signal. In analog signals each value of the signal affects the system Since in digital electronics there are only two logic levels or voltage levels even though the noise is added to the signal it will not affect the digital signal.
2. Portability: Since digital electronics deal with digital data, which can be stored in memory. So it is very portable.
3. Flexibility: Any system built using digital electronics can perform differently by simply changing the digital code which is nothing but the digital logic. So for minor changes in the system performance, we need not change the whole hardware of the system.
4. Accuracy and Precision: In a digital system, any system data is represented by numbers. These numbers are stored in memory. Since now ample memory is available at a very low cost we can represent the system data by numbers with long precision. Since the effect of environmental changes is less in digital electronic systems it gives very accurate results.

Disadvantages of Digital Electronics

Though the digital system has noise immunity and better storage, it does have disadvantages too:

• The energy consumed by the digital system is more compared to the analog system. This energy is consumed in calculations and signal processing, resulting in heat generation.
• These systems are expensive.
• Digital systems are fragile. That is, if one of the digital data is misinterpreted, the final data will change completely.
• Taking care of analog issues in digital systems could be demanding as analog components are used in designing the digital system.

Applications of Digital Electronics

Here are the uses of digital electronics:

• The display of digital watches is designed based on digital circuits.
• Rocket science and quantum computing use digital electronics.
• The automatic doors work on the principle of digital electronics.
• Everyday encounters with traffic lights are based on digital circuits.
• Mobile Phones, Calculators and Digital Computers
• Radios and Communication Devices
• Signal Generator
• Smart Card
• Cathode Ray Oscilloscope(CRO)
• Analog to digital converters (ADC)
• Digital to analog converters (DAC), etc.

Conclusion

• The physical world is analog, but digital techniques are often far superior to analog techniques in the context of electronic design.
• Digital circuits have signals that transition between logic high, which represents binary 1, and logic low, which represents binary 0.