Digital electronics: Basics of digital electronics

Basics of digital electronics:

Basics of digital electronics

Digital systems
A system which deals with quantities and variables having two discrete values or states are called is called digital system. In these circuits, the input and output can have any one of the two values “1” or “0”. Following are the examples of such quantities:

• A switch can either open or closed.
• The answer of a question can be either yes or no.
• A certain statement can be either true or false.
• A bulb can be either on or off.

In all these situations, one of the states is represented by “1” and the other state by “0”.
"1" represents:
i. ON circuit
ii. High voltage
iii. True statement
"0" represents:
i. OFF circuit
ii. Low voltage
iii. False statement

Number systems in digital electronics:

Types of digital circuits:

There are mainly two types of digital circuits-

Combinatorial Circuits: In these circuits, the past states are immaterial

and the output depends only upon the present state. Example: logic gates

Sequential circuits: In these circuits, the next state is completely determined by the past states. Hence these follow a predictable structure and essentially require a timing device. Example: counters, flip flops.

Clock: Building block of a sequential circuit:

A clock is simply alternate high and low states of voltage with time i.e. essentially a square wave.Important terms related to clock are its duty cycle and its frequency:

Duty cycle: It is the ratio of Th and Th+Tl, D=Th/𝑇𝑙+𝑇ℎ

table of logic gates

Logic Gates: Building block of a combinatorial circuit:
These are essentially combinational circuits are used to implement logical Boolean operations like AND, NAND, OR, XOR and NOT. NOT and NAND are called universal gates as any other gate can be formed

using either of them!

Identification of some Practical Circuiting Elements:

Resistance:

A color scheme is followed to give the specifications of a resistor. The table for color code is shown below:

Resistor values are calculated one band at a time,from left to right.Match each band color with the corresponding value on the color chart.The 1st two bands specify the 2 digits of the resistor value whereas the 3 rd band specifies the multiplier in terms of the power to which 10 is raised and multiplied to the 2 digits. 

The tolerance tells the possible % variation of the resistor value about the value indicated by bands.

Inductors:

A color scheme is followed to give the specifications of a inductor. The table for color code is shown below:

Inductors values are calculated one band at a time, from left to right.Match each band color with the corresponding value on the color chart.The 1st two bands specify the 2 digits of the inductors value whereas the 3 rd band specifies the multiplier in terms of the power to which 10 is raised and multiplied to the 2 digits. 

The tolerance tells the possible % variation of the inductor value about the value indicated by bands.

Capacitors:

The 2 types of capacitors we frequently use in circuits are ceramic and electrolytic capacitors. While ceramic capacitors do not have a fixed polarity; electrolytic capacitors should be connected in their specified polarities only else they might blow off! This polarity is usually provided on the side of the capacitors ‘corresponding leg.There's a very useful chart for calculation the right value of Ceramic / Non – Polarized Capacitors given below.

Diodes:

A Diode is a two terminal semiconductor device with a single pn junction,which has the ability to pass current in only one direction.which made of two electrodes called the anode and the cathode.generally cathode is identified by a silver or colored band.

Diode can be used as rectifiers,signal limiters,voltage regulators,switches,signal modulators,signal mixers,signal demodulators or oscillators.

Some of the different types of diodes are:

Rectifier diode: 

These diodes are used to rectify alternating current inputs in power supplies.

Zener diode:

This type of diode provides a stable reference voltage.It's designed to conduct in the reverse direction when the breakdown voltage is reached.

Light Emitting Diode[L.E.D]:

One of the most popular types of diodes.The LED emmits light when diode is in forward bias.The longer lead is the anode(+) and the flat side is the cathode (-).

Photodiodes:

Conduct only when they are exposed to light.



Breadboard:

This is the base used for setting up the circuit. This has embedded metal strips in it that form a grid of connections inside its body. This allows us to take multiple connections from a single point without any need of soldering/disordering as in PCBs. It is always a good habit to test the circuit on breadboard before making it on a PCB.

Top view showing the connecting holes. Bottom view shows the contact metal strips

Integrated circuits [I.C]:

ICs or Integrated Circuits are packaged circuits designed for some fixed purpose. An IC has its fixed IC name/number that can be used to get catalog of its functions and pin configuration. ICs come in various sizes and packages depending upon the purpose.Different ICs may have different number of pins.

Integrated circuit (I.C)