Electronics

Electronics is a field of science and technology that deals with the study and application of electronic devices, circuits, and systems.

• It involves the design, development, and utilization of components such as transistors, diodes, integrated circuits (ICs), and printed circuit boards (PCBs) to create electronic devices and systems for various purposes.
• Electronics plays a crucial role in modern technology, powering devices ranging from smartphones and computers to medical equipment and industrial machinery.
• It encompasses diverse subfields, including analog and digital electronics, microelectronics, power electronics, and telecommunications.
• The continuous advancement of electronics drives innovation in many industries, shaping the way we live, work, and communicate in the digital age.

Basic Math & Calculus

Number Systems & Conversions

Q : Binary number 1101.101 is equivalent to decimal number?
A. 13.5
B. 13.75
C. 13.625
D. 13.875

Answers

Option C: 13.625

Explanation

• Binary 1101 equals in decimal 13 and binary .101 equals 0.625 in decimal

Q: Convert decimal to binary of 88.

Answer

• 88/2 =44 = 0
• 44/2 = 22 = 0
• 22/2=11 = 0 11/2=5 = 1 5/2=2 = 1 2/2=1 = 0

Negative Number Representation

• LSB & MSB: for example 29 decimal to Bianry is 00011101 Here 1(0-th Bit) is Least Significant Bit (LSB) and 0(7th Bit) is Most Significant Bit (MSB)
• One’s Complement: (Invert all bits) So 29 of 1st complement 11100010.
• Two’s Complement: (Add 1 to the result of One’s complement) 111100010 + 1 = 11100011.
• Positive Numbers: Stored as their normal binary form (with leading zeros to fill the bit length).
• Negative Numbers: Stored as the two’s complement of their absolute value. which simplifies arithmetic operations and avoids duplicate representations (like +0/-0).

Q: How is -28 represented in 8-bit two’s complement?

Answers

• Convert 28 to binary: 00011100.
• Invert bits: 11100011.
• Add 1: 11100011 + 1 = 11100100.
• ∴ 11100100 is the 8-bit two’s complement of -28.

Hexadecimal Arithmetic

Q: Calculate 0x1A3 + 0xB7. Express the result in hex. Check for overflow in an 8-bit system.

Answers

• 0x1A3 = 1*256 + 10*16 + 3 = 419
• 0xB7 = 11*16 + 7 = 183
• Sum: 419 + 183 = 602
• Hex equivalent: 602 → 0x25A (since 602 = 2*256 + 5*16 + 10).
• 8-bit overflow? Yes, because 602 > 255 (max 8-bit unsigned value).

Principles of Electric Circuits

Here will learn about Ohm’s Law, Kirchhoff’s Laws, Series/Parallel circuits

Physics

• P-TYPE: Trivalent impurities (3 valence electrons)
  • Aluminum, boron, gallium, and indium.
• N-TYPE: Pentavalent impurities (5 valence electrons)
  • antimony, arsenic, bismuth, and phosphorus.

Atom

• The atom consists of the three-stage of the particles namely electron (outermost of the orbit), and clustered neutron and proton.
• Atoms are a very minute part of the element,
• We cannot visible the atom, the radius of the atom is 1A⁰=10^-10m.

Name	Symbol		Mass(atomic mass unit)	Normal mass(a.m.u)
Electron	E	-1	5.4000000000000001E-4	0
Proton	P	1	1.0072700000000001	1
Nutron	N	0	1.00867	1

Coulomb’s law

1. The force between two charged bodies was studied by Coulomb in 1785.
2. Coulomb’s law states that the force of attraction or repulsion between two point charges is directly proportional to the product of the charges and inversely proportional to the square of the distance between them. The direction of forces is along the line joining the two point charges. Let q1 and q2 be two-point charges placed in air or vacuum at a distance r apart. Then, according to Coulomb’s law,

F αq₁ q₂/r²

or F = k×q₁ q₂/r²

where k is a constant of proportionality. In air or vacuum,

k =1/4πε₀, where εo is the permittivity of free space (i.e., vacuum) value of ε₀ is 8.854 × 10^-12 C² N^-1 m^-2.

Ohm’s Law (1827)

1. George Simon Ohm established the relationship between potential difference and current, which is known as Ohm’s law.
2. At a constant temperature, the steady current flowing through a conductor is directly proportional to the potential difference between the two ends of the conductor.

(i.e) I α V

Kirchhoff

first law (current law)

Kirchhoff’s current law states that the algebraic sum of the currents meeting at any junction in 7 a circuit is zero.

second law (voltage law)

Kirchoff’s voltage law states that the algebraic sum of the products of resistance and current in each part of any closed circuit is equal to the algebraic sum of the emf’s in that closed circuit. This law is a consequence of the conservation of energy.

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Resistance

Resistance of a conductor is defined as the ratio of potential difference across the conductor to the current flowing through it. The unit of resistance is the ohm (Ω). Resistance – The electrical resistance of an electrical conductor is a measure of the difficulty to pass an electric current through that conductor. The inverse quantity is electrical conductance and is the ease with which an electric current passes.

Any conductor’s resistance depends upon the following things

1. Length of the conductor (L).
2. The specific resistance of the nature material (Rho).
3. The cross-sectional area of the conductor(A).

Length Directly is Proportional to Resistance: R ∝ L

The resistance is directly proportional to the length. If the conductor length is longer then resistance is high so current flow is less.

Cross-Sectional Area is inversely Proportional Resistance: R ∝ 1/A (or) R ∝ A^-1.

Specific Resistance of the materials

The specific resistance of the material of a wire is determined by knowing the resistance (P), radius (r), and length (L) of the wire using the expression ρ =Pπr/L

Material	ρ (Ωm) at 20°C	σ (S/m) at 20°C	Temperature coefficient (1/°C) x10^-3
Silver	1.59×10−8	6.30×107	3.8
Copper	1.68×10−8	5.96×107	3.9
Gold	2.44×10−8	4.10×107	3.4
Aluminum	2.82×10−8	3.5×107	3.9
Tungsten	5.60×10−8	1.79×107	4.5
Zinc	5.90×10−8	1.69×107	3.7
Nickel	6.99×10−8	1.43×107	6
Lithium	9.28×10−8	1.08×107	6
Iron	1.0×10−7	1.00×107	5
Platinum	1.06×10−7	9.43×106	3.9
Tin	1.09×10−7	9.17×106	4.5
Lead	2.2×10−7	4.55×106	3.9
Manganin	4.82×10−7	2.07×106	2E-3
Constantan	4.9×10−7	2.04×106	8.0000000000000002E-3
Mercury	9.8×10−7	1.02×106	0.9
Nichrome	1.10×10−6	9.09×105	0.4
Carbon (amorphous)	5×10−4 to 8×10−4	1.25 to 2×103	-0.5

	substance	Nature	Resistivity(ρΩm)
1	Silver	Conductor	1.6×10-8
2	Gold	Conductor
3	Copper	Good conductor	1.7×10-8
4	Aluminum	Good conductor	2.7×10-8
5	Iron	Conductor	10×10-8
6	Steel	Conductor
7	Brass	Conductor
8	bronze	Conductor
9	Mercury	Conductor
10	Dirty water(saltwater)	Conductor
11	graphite	Conductor
12	tungsten		5.5×10-8
13	Germanium	Semiconductor	(0.40)or (0.6Ωm)
14	Silicon	semiconductor	2300
15	Glass	Insulator	1010– 1014
16	neoprene	Insulator
17	Wood	Insulator	108-1011
18	rupper	Insulator	1013-1016
19	Oil	Insulator
20	Fiberglass	Insulator
21	(Dry)cotton	Insulator
22	(dry)wood	Insulator
23	Air	Insulator
24	Plastic	Insulator
25	Pure water	Insulator
26	Quartz	Insulator	1013
27	Teflon	Insulator
28	Nichrome	Resistance material	10-4 Ωm

Example 1:

Copper material ρ (of copper) = 1.7 x 10^-8 Ωm (17 E-9 or 17 EXP-9 when entering it into your calculator in Standard Form, depending on which model you use), L (Length of cable) = 7m and d (Diameter of cable) = 0.5mm(500 E-6 or 500 EXP-6 meters in Standard Form. so Find the resistance??

Answer

• A (Cross Sectional Area of cable in square metres) = π(d/2²) = 3.142 x ((500 EXP^-6/2)²) = 196.4 EXP^-9m^2.
• Therefore R = (ρL) / A = (17 EXP^-9 x 7) / 196.4 EXP^-9 = 605mΩ

Example 2 :

A wire 12m long has a resistance of 1.5 Ω. What will be the resistance of 16m of the same wire?

Answer

2 Ω

Example 3

A sample of copper wire of 0.2mm radius has a length of 5m. If the resistivity of the copper is 1.7 x 10^-8, what would be the resistance of the wire?

Answer

0.676Ω

Example 4

What is the resistance of 100m of copper wire, having a diameter of 1.024mm?

Answer

2.06Ω

Example 5

The resistance of a 50m length of wire is found to be 0.83 ohms. Its diameter is 1.15mm. What is its resistivity and from what metal is it most probably made?

Answer

1.72 x 10^-8 copper

Conductance

The reciprocal of resistance is conductance. It’s unit is mho (Ω–1)

Current

Electrons flow in a conductor

Eg: water flow in a pipeline.

• 1amps= 6.25*10¹⁸=(6,250,000,000,000,000,000) electrons/second,

Voltage

We define voltage as the amount of potential energy between two points on a circuit. One point has more charge than another. This difference in charge between the two points is called voltage. It is measured in volts, which, technically, is the potential energy difference between two points that will impart one joule of energy per coulomb of charge that passes through it (don’t panic if this makes no sense, all will be explained). The unit “volt” is named after the Italian physicist Alessandro Volta who invented what is considered the first chemical battery. Voltage is represented in equations and schematics by the letter “V”.

When describing voltage, current, and resistance, a common analogy is a water tank. In this analogy, charge is represented by the water amount, voltage is represented by the water pressure, and current is represented by the water flow. So for this analogy, remember:

• Water = Charge
• Pressure = Voltage
• Flow = Current

Consider a water tank at a certain height above the ground. At the bottom of this tank, there is a hose.

Electronics Fundamentals

• Diodes, Transistors, Op-Amps, Capacitors, Resistors

Electronics devises Types

Generally two types Active and Passive Components

• Active Components
  • Semiconductors
  • Diode
  • Transistors
  • Integrated Circuits
  • Optoelectronics Devices
  • Display technologies
  • Vacuum tubes (Valves)
  • Discharge device
  • Power Sources
• Passive Components
  • Resistors
    • What is Resistance?
    • Resistor – Tutorial
  • Capacitors
  • Magnetic Devices (Inductive)
  • Memristor
  • Networks
  • Transducers, Sensors, Detectors
  • Antennas
  • Assemblies, Modules
  • Prototyping Aids
• Electromechanical
  • Piezoelectric devices, Crystals, resonators
  • Terminals and Connectors
  • Cable Assemblies
  • Switches
  • Protection Devices
  • Mechanical Accessories

Diode

• Conduct electricity (Electrons) easily in one direction
• Two lead semiconductor
• Diodes are made by Silicon [mostly], Selenium, and germanium [Sometimes]
• A PN-junction diode is formed by joining together n-type and p-type silicon.
• In practice, as the n-type Si crystal is being grown, the process is abruptly altered to grow p-type Si crystal. Finally, a glass or plastic coating is placed around the joined crystal.
• The p-side is called the anode and the n-side is called the cathode.
• When the anode and cathode of a PN-junction diode are connected to an external voltage such that the potential at the anode is higher than the potential at the cathode, the diode is said to be forward-biased.
• –In a forward-biased diode current is allowed to flow through the device.
• •When the potential at the anode is smaller than the potential at the cathode, the diode is said to be reverse biased. In a reverse-biased diode current is blocked.
• Various Diodes
  • Avalanche Diode
  • Constant Current Diode
  • Crystal Diode
  • Gunn Diode
  • LASER Diode
  • Light Emitting Diode(LED)
  • Photo-Diode
  • PIN Diode
  • Shockley Diode
  • Step Recovery Diode
  • Super Barrier Diode
  • Transient Voltage Suppression Diode (TVS)
  • Tunnel Diode
  • Thermal Diode
  • Vacuum Diode
  • Varactor Diode (Varicap)
  • Zener Diode

Transistors

• Two Types: PNP and NPN. A transistor can be used as a switch, amplifier. β = Ic/Ib. Example Ic = 0.5 to 1.5mA, Ib= 20-40uA, what is β=? (Answer β = 50.)

BJT

• BJT – Bipolar Junction Transistor Application like DC to AC Converter, Induction Motor driver, UPS, SMPS, Chopper

Filter

• Electronic filters are circuits, which perform, signal processing functions, specifically to remove unwanted frequency components from the signal, to enhance wanted ones, or both.
• Types
  • High pass filter
  • Low pass filter
  • Band-pass filter
  • Bandstop filter

RC Filter

First-order RC-filter (high/low pass filter)

• The cut-off frequency is defined as the frequency at which the voltage at the output of the filter is 3dB below the input. In other words, the output signal is 70.7% or 1/sqrt(2) below the input signal.
• For a first-order RC-filter the cut-off frequency (FC) is calculated as follows:
• R1 * C1 = 1/ω = 1/ (2 π fc)
• The time constant ω is equivalent to 2 π FC. Engineers prefer to use FC while many scientists use ω.a

LC Filter

• Low pass- π filters
• High Pass T Filter

Filters Type:

• Capacitor filter
• Choke input filter
• Capacitor input filter or π filter

Oscillators

What is Oscillator? : Oscillator is the heartbeat of every microcontroller design.

Types of Transistor oscillators

• Tuned collector oscillator
• Colpitt’s oscillator
• Hartley oscillator
• Phase shift oscillator
• Wein bridge oscillator
• Crystal oscillator: Its used for demand precise timing over a wide temperature range.

Oscillator for MCU and MPU

• Internal
  • Usually (as far as I know, always) a resistor-capacitor circuit.
  • Phase-locked loop for frequency multiplication
• External
  • CMOS clock
  • Crystal
  • Ceramic resonator
  • Resistor-capacitor,
  • capacitor only

Quartz and ceramic oscillator

• CL-total = ((CL1* CL2)/ CL1+CL2) + Cp
• Cp – Parasitic capacitance
• CL1, CL2 – Load Capacitance

Transducer

Types of transducer

• Pressure Transducers
• Vacuum pressure Transducers
• Melt Pressure Transducers
• submersible Transducers
• linear position Transducers
• Non-contact Linear Transducers
• wireless Transducers
• In-cylinder Linear Transducers

Transformer

Type of Transformer

• Power transformer
• The audio frequency transformer(AFT)
• Radiofrequency transformer(RFT)
• Intermediate frequency transformer(IFT)
• Autotransformer
• Isolation transformer
• Driver transformer

Relay

Relay is an electromagnetically operated switch. Its is an automatic switch. it working in an electromagnetic field. all electronic circuit is ex specially design and fabricated two switches on or switch off the one or more device. all electronic circuit has an end width relay.

Applications of Relay

• Automotive Electronics
  • Mini Plug-in Power Relays
  • Micro Plug-in Relays
  • Enclosed / Sealed Automotive Relays
  • Miniature PCB Automotive Relays and
  • Twin Automotive Relays
• Industrial Instrumentation & Controls
• High-end Consumer Electronics
  • Air Conditioner
  • Heater
• Communications
  • Telecommunication system
• Strategic Electronics

Car LED flasher Relay

• 3-Pin Car LED Flasher Relay Fix Turn Signal – Black (DC 12V)
• 6pin Flasher Relay for All 4 Wheeler Use 12V Dhuale Head Lamp Relay

SCR

• Applications
  • AC to Dc converter
  • AC Converter
  • Electronics Circuit Breaker

MOSFET

• Application
  • DC Choppers,
  • Low power UPS
  • SMPS
  • Brushless DC Motor Drivers

Switch Type

• Pressure Switches
• Temperature Switches
• Flow Switches & Meters
• Liquid Level Switches

Sensor

Sensor Type

• switching sensor
• variable sensor
• image-processing sensor
• RF sensor

Varies Types of Sensor

• Accelerometer Sensor
• Alcohol Sensor
• Current Sensor
• Dew Sensor
• Distance Sensor
• Eye Capture Sensor
• Eye Image Print Sensor
• Figure Print Sensor
• Flow Control (Water Pressure)
• GPS Sensor Module
• Gsm Sensor Module
• Heart Beat Monitor
• Humidity Sensor
• Load Cell
• Luminance Sensor
• Pressure Sensor
• Proximity Sensor
• Solenoid Load
• Temperature Sensor
• Ultra Sonic Sensor
• Vibration Sensor
• Water Solenoid 

Electronics Equipment

Electronics Engineer Must have following Equipment

• Scale
• Multimeter
• Soldering iron
• Oscilloscope
• Vernier caliber

Symbol Pb & RoHs

What is this symbol mean by Pb?

• Lead-Free & RoHS Compliant Label solutions

What is RoHS?

• RoHS (Restriction of Hazardous Substances) is a European Union directive that restricts the use of lead, mercury, cadmium, chromium (VI), PBBs, and PBDEs in electrical and electronic equipment as of July 1, 2006.

Digital Electronics

Digital electronics is a branch of electronics that deals with the study, design, and implementation of digital circuits, systems, and devices. Unlike analog electronics, which deals with continuous signals, digital electronics processes and manipulates discrete signals represented by binary digits (bits) – 0s and 1s.

Digital electronics focuses on the design and analysis of digital circuits and systems that perform logical operations and arithmetic computations using binary numbers. It involves the use of digital components such as logic gates, flip-flops, registers, counters, and microcontrollers to build digital systems capable of processing, storing, and transmitting information in digital form.

Digital electronics is fundamental to modern technology, playing a crucial role in various applications, including computing, telecommunications, digital signal processing, control systems, and consumer electronics. It forms the basis of digital computers, smartphones, digital cameras, digital audio players, and many other digital devices that are pervasive in our daily lives.

Key concepts in digital electronics include Boolean algebra, logic gates, truth tables, combinational and sequential logic circuits, finite state machines, and digital signal processing techniques. Digital electronics also encompasses advanced topics such as microprocessor and microcontroller programming, digital communication protocols, and digital system design methodologies.

Overall, digital electronics is a cornerstone of modern technology, enabling the development of sophisticated digital systems that drive innovation and shape the digital world we live in.

Bit, Nibble, Byte, word

• Bit – Single bit
• Nibble – Four bits
• Byte – Eight bits
• Word – Sixteen bits

The below image can make understand clearly about

What is the difference of All ?

Bit, Byte, Nibble, Word, Kilobyte(KB), Megabyte(MB), Gigabyte(GB), Terabytes(TB).

• Bit: A bit is the smallest unit if information that can be stored in a computer. Bits in computer are grouped to form a lager unit of information
• Byte: A byte is a combination of eight bits. Eight bits represent a character and is called a byte.
• Nibble: A nibble is a combination of four bits, in other words a nibble is half a byte.
• Word: a word is a combination of 16 bits, 32 bits or 64 bits depending on the computer. 16 is known as quad word.
• Kilobyte (kb): A kilobyte has a memory unit of 1024 (2**10)
• Megabyte: a megabyte has a memory unit if 1,048,576 (2**20). This is approximately 1 million bytes.
• Gigabytes (gb): A gigabyte has a memory unit of 1,073,741,824 (2**30). This approximately billion bytes.
• Terabytes: a terabyte has a memory unit of (2**40). This is approximately 1 trillion bytes.

Note:

• 1024 byte = 1 kilobyte (1kb)
• 1024 kilobytes = 1 megabytes (1mb)
• 1024 megabyte = 1 gigabytes (1 Gb)
• 1024 gigabytes =1 terabyte (1tb)

Logic Gates

• NOT
• AND
• NAND
• OR
• NOR
• XOR
• XNOR

Truth Tables

NOT

Bit	Result
0	1
1	0

AND, NAND, OR, NOR, XOR, XNOR

Bit-1	Bit0	AND	NAND	OR	NOR	XOR	XNOR
0	0	0	1	0	1	0	1
0	1	0	1	1	0	1	0
1	0	0	1	1	0	1	0
1	1	1	0	1	0	0	1

FlipFlops

• SR Flipflop
• JK Flipflop
• D FlipFlop
• T Flipflop

SR Flipflop

S	R	Q	Q’
0	0	0	1
0	1	0	1
1	0	1	0
1	1	∞	∞

JK Flipflop

J	K	Q	Q’
0	0	0	0
0	1	0	0
1	0	0	1
1	1	0	1
0	0	1	1
0	1	1	0
1	0	1	1
1	1	1	0

D Flipflop

Clock	D	Q	Q’
↓ » 0	0	0	1
↑ » 1	0	0	1
↓ » 0	1	0	1
↑ » 1	1	1	0

T FlipFlop

T	Q	Q (t+1)
0	0	0
1	0	1
0	1	1
1	1	0

Applications of Flip-Flops

• Counters
• Frequency Dividers
• Shift Registers
• Storage Registers

Parity Checker

• Two Types
  • Odd Parity Bit
  • Even Parity Bit

Cyclic Redundancy Checker

• The CRC was invented by W. Wesley Peterson in 1961
• The 32-bit CRC function, used in Ethernet and many other standards.

VLSI

• NOT Gate using NMOS and PMOS
• AND Gate using NMOS and PMOS
• OR Gate using NMOS and PMOS
• NAND Gate using NMOS and PMOS
• NOR Gate using NMOS and PMOS
• XOR Gate using NMOS and PMOS
• XNOR Gate using NMOS and PMOS

Computer Architecture

• Registers, ALU, Memory hierarchy, Instruction cycle

CPU

CPU is the central processing unit, it’s the heart of the system.

If you wanna see how the CPU works? there is a web-based simulator available in internet. On this site, you can load your source file of your respective processor and see live to understand how the CPU is working.

ALU

ALU is an Arithmetic Logical Unit. CPU consists of the ALU.

Computer

types of Computer

1. Super Computer(Ex: Research Using purpose)
2. Main frame computer (E-Banking, E-Tickets)
3. Mini Computer
4. Micro Computer(Work Station, Personal Computer, Laptop, Palm PC’s)

Computer input Devices	Computer Output Devices
Mouse Keyboard Scanner Bar Code Reader – BCR Magnetic Ink Character Recognition – MICR Magnetic Card Reader (ATM Debit Card) Microphone	Monitor Printers

Computers Storage

1. Primary Storage
   • ROM (PROM, EPROM, EEPROM)
   • RAM (SRAM, DRAM) Here, RAM- Random Access Memory.
2. Secondary Storage
   • Hard Disk
   • Floppy Disk
   • CD
   • Pen Drive
   • Memory Card

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OS

Operating System types

1. Character User Interface-CUI (Ex : MS DOS)
2. Graphical User Interface – GUI (Ex : MS Windows)

Windows Operating System

• introduced by apple company and developed by Microsoft

Windows XP

• Logging in – enter your passwords to login
• Logging Off (press Control + L )

Different Between x86 and x64

• x86 for 32 OS (32-bit system cant run 64bit application. 32 Application only possible to run)
• x64 for 64bit OS (64-Bit system can run both 32 and 64 bit applications)

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IP Address

IPV4 Address Classes (Pre 1993 Mindset)

• Class A:  Range 1.0.01 to 126.255.255.254, Speed 16M host 127 Networks, Default Subnet Mask 255.0.0.0, IP Address 0-126.
• Class B:  Range 128.1.0.1 to 191.255.255.254, Speed 64K host 16K Networks, Default Subnet Mask 255.255.0.0, IP Address 128-191.
• Class C:  Range 192.0.1.1 to 223.255.254.254, Speed 254 Host 2M Networks, Default Subnet Mask 255.255.255.0, IP Address 192-223
• Class D:  Range 224.0.0.0 to 239.255.255.255, Speed Multicast. , Default Subnet Mask N/A, IP Address 224-239.
• Class E:  Range 240.0.0 to 254.255.255.254, R&D == Wasted, Default Subnet Mask N/A, IP Address 240-255.

 

OTHERS

Electronics Tutorials – 230v Single LED Circuit

This is a simple circuit and can use 230v AC LED indication in a home that can be directly powered from mains. To make this by three simple electronics components Resistor, Diode and LED But it’s not isolated so very dangerous, if you have not good knowledge about AC circuit please don’t try. these following circuits are reverse circuit from extension box

Method-1

Required Components

• Diode 1N4007 – 1 Nos
• Resistor 270k Ohm 5% – 1 Nos
• Red LED 2v (633mm) – 1 Nos
• Wires

Schematics

Circuit

Electronics hardware Guide.

If your doing the electronics hardware troubleshooting then you need to carefully taken care of the thing.

IC Replacement Guidelines

for example, one IC was damaged in the board, if you replace it with a new IC then after re-soldered that, you need to carefully check the continuity test for all nearby pins like 1 and 2 sort is there or not? 2 and 3 sorts or not like. Refer to the pin details of the IC also.