Electronics Components, Devices and Circuits
In this post we include given below topic for readers. It's help to cover wireless PSI all topics step by step.
1. Conducting Materials
2. Magnetic Materials
3. Insulating Materials
4. Semiconductors
5. Semiconductors physics and diode
Conducting Materials
When discussing the flow of electricity through materials, two key concepts come up:
conductivity and resistivity
They are essentially opposite sides of the same coin. Here's a breakdown:
Resistivity (ρ):
This is a measure of how strongly a material opposes the flow of electric current.
A high resistivity means the material is a poor conductor of electricity (an insulator).
A low resistivity means the material is a good conductor.
The unit of resistivity is ohm-meters (Ω⋅m).
Conductivity (σ):
This is a measure of how easily a material allows electric current to flow.
A high conductivity means the material is a good conductor.
A low conductivity means the material is a poor conductor (an insulator).
The unit of conductivity is siemens per meter (S/m).
The Relationship:
Conductivity and resistivity are inversely proportional to each other. This means:
If resistivity is high, conductivity is low.
If resistivity is low, conductivity is high.
Mathematically, this is expressed as: σ = 1/ρ or ρ = 1/σ.
In simpler terms:
Think of resistivity as a traffic jam: the higher the resistivity, the more difficult it is for cars (electrons) to move.
Think of conductivity as a smooth, open highway: the higher the conductivity, the easier it is for cars to move.
Key points to remember:
These are material properties, meaning they describe the inherent ability of a substance to conduct electricity.
Materials like copper and silver have high conductivity and low resistivity, making them excellent conductors.
Materials like rubber and glass have low conductivity and high resistivity, making them excellent insulators.
Temperature coefficient
The effect of temperature on the electrical properties of materials varies significantly depending on whether the material is a conductor, insulator, or semiconductor. Here's a breakdown:
1. Conductors:
Increased Temperature:
In conductors (primarily metals), increasing temperature leads to an increase in resistance.
This occurs because higher temperatures cause atoms within the material to vibrate more vigorously. These vibrations disrupt the flow of free electrons, leading to more collisions and therefore increased resistance.
This is described as having a positive temperature coefficient.
Decreased Temperature:
Conversely, decreasing temperature reduces atomic vibrations, allowing electrons to flow more freely, which results in lower resistance.
2. Insulators:
Increased Temperature:
In insulators, the effect of temperature is somewhat opposite to that of conductors.
As temperature increases, the resistance of insulators tends to decrease, and their conductivity increases.
This is because higher temperatures can provide enough energy for some electrons to break free from their bonds and contribute to conduction. However, even at higher temperatures, insulators remain poor conductors compared to metals.
Decreased Temperature:
Decreasing temprature increases the resistance of the insulator.
3. Semiconductors:
Increased Temperature:
Semiconductors exhibit a unique temperature dependence.
As temperature increases, the conductivity of semiconductors increases, and their resistance decreases.
This is because higher temperatures generate more free charge carriers (electrons and holes), which significantly enhance conductivity.
Semiconductors have a negative temperature coefficient.
Decreased Temperature:
Decreasing temperature reduces the availability of free charge carriers, therefore reducing conductivity, and increasing resistance.
In summary:
Conductors: Resistance increases with temperature.
Insulators: Resistance decreases with temperature.
Semiconductors: Resistance decreases with temperature.
These temperature dependencies are crucial in various electronic applications, from designing temperature sensors to ensuring the reliable operation of electronic devices in different environments.
Here is Some MIMP Mcq which can be asked in Government Job exam.
Question 1
What is the effect of increasing temperature on the resistance of a conductor (e.g., copper)?
A) Decreases
B) Increases
C) Remains constant
D) Becomes zero
Answer:B) Increases
Question 2
What happens to the resistance of a semiconductor (e.g., silicon) as temperature increases?
A) Increases
B) Decreases
C) Remains constant
D) Becomes infinite
Answer: B) Decreases
Question 3
Which material has a positive temperature coefficient?
A) Silicon
B) Copper
C) Germanium
D) Ceramic
Answer: B) Copper
Resistance colour coding
| Colour | First Digit | Multiplier | Tolerance |
|---|---|---|---|
| Black | 0 | 100 |
|
| Brown | 1 | 101 | |
| Red | 2 | 102 | |
| Orange | 3 | 103 | |
| Yellow | 4 | 104 | |
| Green | 5 | 105 | |
| Blue | 6 | 106 | |
| Violet | 7 | 107 | |
| Grey | 8 | 108 | |
| White | 9 | 109 | |
| Gold | 10-1 | +-5% | |
| Silver | 10-2 | +-10% | |
| No Colour | +-20% |
Here is Some MIMP Mcq which can be asked in Government Job exam.
Q 1:Which of the following factors does resistivity of materials depends?
A. Temperature
B. Length of the conductor
C. Nature of material
D. All of the above
Answer:- D. All of the above
Q 2:A perfect Conductor has....
A. Zero Conductivity
B. Unity Conductivity
C. Infinite Conductivity
D. None of these
Answer:- C. Infinite Conductivity
Semiconductor
There are mainly 2 types of semiconductor.
P type and N type.
P -Type semiconductor
A p-type semiconductor is a type of extrinsic semiconductor formed by doping an intrinsic (pure) semiconductor with a trivalent impurity. Here's a breakdown:
Intrinsic Semiconductors:
Pure semiconductors like silicon (Si) or germanium (Ge) have four valence electrons. In their crystal lattice, each atom forms covalent bonds with its four neighboring atoms.
At room temperature, these semiconductors have a limited number of free electrons and holes (electron vacancies), resulting in low electrical conductivity.
Doping to Create a P-type Semiconductor:
To create a p-type semiconductor, a small amount of a trivalent impurity is added to the intrinsic semiconductor. Trivalent impurities are elements with three valence electrons, such as:
• Boron (B)
• Aluminum (Al)
• Gallium (Ga)
• Indium (In)
When a trivalent atom replaces a silicon or germanium atom in the crystal lattice, its three valence electrons form covalent bonds with three of the neighboring semiconductor atoms. This leaves one bond without an electron, creating a hole (an electron vacancy).
Charge Carriers in P-type Semiconductors:
The introduction of trivalent impurities creates a significant number of holes in the valence band.
These holes are mobile and can move through the crystal lattice as electrons from nearby bonds jump to fill them, leaving a new hole behind.
In a p-type semiconductor, holes are the majority charge carriers, and electrons are the minority charge carriers (due to thermal excitation).
The "p" in p-type stands for "positive," referring to the positive charge associated with the holes.
Properties of P-type Semiconductors:
* Majority Carriers: Holes
* Minority Carriers: Electrons
* Higher Conductivity: P-type semiconductors have significantly higher electrical conductivity than intrinsic semiconductors due to the increased concentration of mobile holes.
* Fermi Level: The Fermi level in a p-type semiconductor is closer to the valence band than the conduction band.
* Neutral Charge: Although there is an abundance of holes, the p-type semiconductor material as a whole remains electrically neutral because the number of protons in the nuclei equals the total number of electrons in the atoms.
Applications of P-type Semiconductors:
P-type semiconductors are crucial components in various electronic devices, including:
Diodes: Used in conjunction with n-type semiconductors to create p-n junctions, which allow current to flow in only one direction.
Transistors: Used in bipolar junction transistors (BJTs) and field-effect transistors (FETs) for amplification and switching.
Solar Cells: Used to absorb light and generate electron-hole pairs, which are then separated to create an electric current.
Integrated Circuits (ICs): P-type regions are essential for creating various components within microchips.
N -Type semiconductor
An n-type semiconductor is a type of extrinsic semiconductor created by doping an intrinsic (pure) semiconductor with a pentavalent impurity. Here's a detailed explanation:
Intrinsic Semiconductors:
Pure semiconductors like silicon (Si) or germanium (Ge) have four valence electrons. These electrons form covalent bonds within the crystal lattice, resulting in limited electrical conductivity at room temperature due to a small number of thermally generated free electrons and holes.
Doping to Create an N-type Semiconductor:
To create an n-type semiconductor, a small amount of a pentavalent impurity is added to the intrinsic semiconductor. Pentavalent impurities are elements with five valence electrons, such as:
• Phosphorus (P)
• Arsenic (As)
• Antimony (Sb)
• Bismuth (Bi)
When a pentavalent atom replaces a silicon or germanium atom in the crystal lattice, four of its five valence electrons form covalent bonds with the four neighboring semiconductor atoms. The fifth valence electron is left over and is loosely bound to the impurity atom.
This extra electron requires very little energy to detach from the impurity atom and move into the conduction band, becoming a free electron that can contribute to electrical conductivity.
Charge Carriers in N-type Semiconductors:
The introduction of pentavalent impurities significantly increases the concentration of free electrons in the conduction band.
In an n-type semiconductor, electrons are the majority charge carriers, and holes are the minority charge carriers (due to thermal excitation).
The "n" in n-type stands for "negative," referring to the negative charge of the electrons.
Properties of N-type Semiconductors:
* Majority Carriers: Electrons
* Minority Carriers: Holes
* Higher Conductivity: N-type semiconductors have much higher electrical conductivity than intrinsic semiconductors because of the large number of mobile electrons.
* Fermi Level: The Fermi level in an n-type semiconductor is closer to the conduction band than the valence band.
* Neutral Charge: Despite the abundance of free electrons, the n-type semiconductor material as a whole remains electrically neutral. This is because each pentavalent impurity atom contributes one free electron but also leaves behind a positively charged ion (the atom's nucleus with its remaining four valence electrons tightly bonded). The total positive charge of these ions equals the total negative charge of the free electrons.
Applications of N-type Semiconductors:
N-type semiconductors are fundamental components in a wide range of electronic devices, including:
* Diodes: Used with p-type semiconductors to form p-n junctions, which are essential for creating diodes that allow current flow in one direction.
* Transistors: Used in bipolar junction transistors (BJTs) as the emitter and collector regions and in field-effect transistors (FETs) as the source and drain regions for amplification and switching.
* Solar Cells: Often used as one of the layers in solar cells to facilitate the separation and collection of photogenerated electrons.
* Light Emitting Diodes (LEDs): Used in the n-type layer of the p-n junction that emits light when current flows through it.
* Integrated Circuits (ICs): N-type regions are crucial for creating various components and interconnections within microchips.
* Photodetectors: The increased electron concentration makes n-type materials useful in devices that detect light by measuring the change in conductivity due to absorbed photons.
Electronic components
Electronic components are the building blocks of electronic circuits and devices. They are designed to perform specific functions when connected together, such as controlling current, storing energy, amplifying signals, or processing data.
They can generally be classified into two main categories:
1. Passive Components:
These components do not require an external power source to operate and cannot amplify or generate an electrical current. They primarily consume, store, or release electrical energy.
Resistors: Limit or oppose the flow of current in a circuit. Used in voltage dividers, current limiters, and to set biases. Measured in Ohms (\Omega).
Capacitors: Store electrical energy in an electric field. Used for filtering, smoothing power supplies, timing circuits, and coupling/decoupling signals. Measured in Farads (F)
Inductors (Coils): Store energy in a magnetic field. Used in filters, chokes, transformers, and oscillators. Measured in Henries (H).
Transformers: Transfer electrical energy between circuits, often used to step up or step down AC voltage.
2. Active Components:
These components require an external power source to operate and can amplify, rectify, or convert electrical energy. They are capable of controlling or manipulating the flow of electricity.
Diodes: Semiconductor devices that allow current to flow primarily in one direction. Used for rectification (converting AC to DC), voltage stabilization (Zener diodes), and signal detection. Light-Emitting Diodes (LEDs) are a common type of diode that emits light.
Transistors: Fundamental building blocks of modern electronics. They act as electronic switches or amplifiers for electrical signals. Types include Bipolar Junction Transistors (BJTs) and Field-Effect Transistors (FETs).
Integrated Circuits (ICs): Microelectronic devices that combine multiple electronic components (transistors, resistors, capacitors, etc.) onto a single semiconductor chip. They are essentially miniature circuits and range from simple logic gates to complex microprocessors and microcontrollers.
Operational Amplifiers (Op-Amps): High-gain electronic voltage amplifier DC-coupled devices. Used in a wide range of applications, including signal amplification, filtering, and mathematical operations.
Other Important Electronic Components:
Switches: Mechanical or electronic devices used to open or close an electrical circuit, controlling the flow of current.
Sensors: Convert physical phenomena (like temperature, light, pressure) into electrical signals.
Connectors: Devices that join electrical conductors to create a continuous electrical path.
Batteries: Store chemical energy and convert it into electrical energy to provide a DC power source.
Fuses: Safety devices that protect circuits from overcurrent conditions by melting and breaking the circuit.
Crystals and Resonators: Provide a stable clock signal for electronic circuits, especially in microcontrollers and watches.
Displays: Output interfaces that transform electrical signals into visual output (e.g., LEDs, LCDs).
Microcontrollers: Miniature computers on a single integrated circuit that contain a processor, memory, and input/output peripherals, often used in embedded systems.
Understanding these basic electronic components and their functions is crucial for anyone involved in designing, building, or troubleshooting electronic circuits.
Semiconductors physics and diode
Semiconductor physics is a fascinating field that underpins almost all modern electronics, from the smartphone in your pocket to the supercomputers driving scientific discovery. At its core, it deals with materials that have electrical conductivity between that of a good conductor (like copper) and an insulator (like glass). This unique property allows us to control the flow of electricity in ways that are impossible with simple conductors or insulators.
Here's a breakdown of semiconductor physics and how it applies to diodes:
Semiconductor Physics
1. What are Semiconductors?
Semiconductors are typically crystalline solids, most commonly Silicon (Si) and Germanium (Ge), but also compounds like Gallium Arsenide (GaAs). Their defining characteristic is that their electrical conductivity can be significantly altered by:
Temperature: At very low temperatures, semiconductors behave like insulators. As temperature increases, more electrons gain enough energy to break free and contribute to conduction.
Light: Certain semiconductors are sensitive to light, leading to devices like photodiodes and solar cells.
Impurities (Doping): This is the most crucial aspect. By adding tiny amounts of specific impurity atoms to a pure (intrinsic) semiconductor, we can drastically change its conductivity and create either:
N-type semiconductors: Doped with pentavalent impurities (e.g., Phosphorus, Arsenic) that have 5 valence electrons. Four of these electrons form covalent bonds with the semiconductor atoms, leaving one "extra" electron that is loosely bound and can easily become a free electron, making electrons the majority charge carriers.
P-type semiconductors: Doped with trivalent impurities (e.g., Boron, Indium) that have 3 valence electrons. These atoms form covalent bonds but create a "hole" (a missing electron in a covalent bond) that can easily accept an electron, making holes the majority charge carriers.
2. Charge Carriers: Electrons and Holes
In semiconductors, current is carried by two types of charge carriers:
Electrons: Negatively charged particles that are free to move in the material's crystal lattice.
Holes: Conceptually, these are positively charged "vacancies" where an electron is missing from a covalent bond. When an electron moves to fill a hole, it creates a new hole in its previous position, effectively making the hole "move" in the opposite direction.
3. Energy Bands
The behavior of electrons in a semiconductor is best understood using the concept of energy bands:
Valence Band (VB): Contains electrons that are tightly bound to atoms and are involved in covalent bonds.
Conduction Band (CB): Contains electrons that have enough energy to break free from their atoms and move freely through the material, contributing to electrical current.
Forbidden Energy Gap (Band Gap): The energy difference between the top of the valence band and the bottom of the conduction band. In insulators, this gap is very large, making it difficult for electrons to move to the conduction band. In conductors, the valence and conduction bands overlap. In semiconductors, the band gap is moderate, allowing some electrons to jump to the conduction band, especially with increased temperature or doping.
Diodes
A diode is one of the simplest and most fundamental semiconductor devices. Its primary function is to allow electric current to flow predominantly in one direction while blocking it in the opposite direction. This unidirectional behavior is achieved by creating a p-n junction.
How a p-n Junction (Diode) Works:
Formation of the p-n Junction: When a p-type semiconductor material is joined to an n-type semiconductor material, a p-n junction is formed. It's not simply two pieces glued together; rather, a single crystal is doped differently on either side.
Depletion Region (at equilibrium/no bias):
At the moment of contact, the high concentration of free electrons in the n-side causes them to diffuse across the junction to the p-side, where they recombine with holes.
Similarly, holes from the p-side diffuse to the n-side and recombine with electrons.
As electrons leave the n-side, they leave behind positively charged donor ions (immobile). As holes leave the p-side, they leave behind negatively charged acceptor ions (immobile).
This diffusion process creates a region near the junction that is "depleted" of free charge carriers (electrons and holes). This region is called the depletion region or space-charge region.
The immobile positive and negative ions create an internal electric field across the depletion region, which opposes further diffusion of charge carriers. This electric field results in a built-in potential barrier (typically around 0.7V for silicon and 0.3V for germanium).
Forward Bias (Current ON):
When an external voltage is applied such that the positive terminal of the battery is connected to the p-side (anode) and the negative terminal to the n-side (cathode), the diode is said to be forward-biased.
The applied voltage's electric field opposes the built-in electric field of the depletion region.
If the applied forward voltage exceeds the built-in potential barrier, the depletion region narrows significantly.
This reduction in the barrier allows majority carriers (electrons from n-side, holes from p-side) to easily flow across the junction, resulting in a large current.
Reverse Bias (Current OFF):
When an external voltage is applied such that the negative terminal of the battery is connected to the p-side (anode) and the positive terminal to the n-side (cathode), the diode is said to be reverse-biased.
The applied voltage's electric field acts in the same direction as the built-in electric field, strengthening it.
This causes the majority carriers to be pulled away from the junction, widening the depletion region.
The wider depletion region and stronger electric field create a very high resistance, effectively blocking the flow of current. Only a very small leakage current (reverse saturation current) flows due to minority carriers.
If the reverse bias voltage is increased too much, it can reach a breakdown voltage, where a large current suddenly flows (e.g., in Zener diodes, this is a controlled breakdown used for voltage regulation).
A diode is a fundamental two-terminal electronic component that acts primarily as a one-way switch for electric current. It allows current to flow easily in one direction (forward bias) but significantly restricts or blocks current flow in the opposite direction (reverse bias).
How it Works:
Most modern diodes are semiconductor diodes, typically made from silicon, and are based on a p-n junction.
Key Characteristics:
Anode and Cathode: Diodes have polarity, with the anode being the positive terminal and the cathode being the negative terminal. Current flows from anode to cathode in forward bias.
Forward Voltage Drop: The voltage drop across the diode when it is conducting in forward bias.
Reverse Breakdown Voltage: The maximum reverse voltage a diode can withstand before it starts conducting in the reverse direction.
Types of Diodes:
There are various types of diodes, each designed for specific applications:
Rectifier Diodes: Used to convert alternating current (AC) into pulsating direct current (DC). They are fundamental in power supplies.
Zener Diodes: Designed to operate reliably in reverse breakdown. They are used for voltage regulation and protection against overvoltage.
Light-Emitting Diodes (LEDs): Emit light when forward-biased current flows through them. Widely used in displays, indicators, and lighting.
Schottky Diodes: Known for their fast switching capabilities and low forward voltage drop, making them suitable for high-speed applications.
Photodiodes: Generate an electrical current when exposed to light. Used in light sensors, solar cells, and optical communication.
Varactor (or Varicap) Diodes: Their capacitance changes based on the voltage applied to them, used in electronic tuning circuits.
Tunnel Diodes: Operate on the principle of quantum mechanical tunneling, used in very high-frequency applications.
Transient Voltage Suppressor (TVS) Diodes: Designed to protect sensitive electronic circuits from high voltage spikes.
Applications of Diodes:
Due to their unidirectional current flow property, diodes are used extensively in electronics for:
Rectification: Converting alternating current (AC) to direct current (DC) in power supplies.
Voltage Regulation: Zener diodes are
specifically designed to maintain a constant voltage across their terminals when reverse-biased beyond a certain point.
Signal Demodulation/Detection: Extracting information from modulated radio waves.
Switching: Acting as electronic switches in various circuits.
Protection: Protecting circuits from reverse voltage or over-voltage.
Light Emission (LEDs): In Light Emitting Diodes (LEDs), when electrons and holes recombine in a forward-biased direct bandgap semiconductor, they emit photons (light).
Light Detection (Photodiodes): In photodiodes, incident light creates electron-hole pairs, which are then separated by the built-in electric field, generating a current.
In summary, semiconductor physics provides the fundamental understanding of how materials like silicon can be engineered to control electrical conductivity. This knowledge is then applied to create essential electronic components like the diode, which acts as a one-way valve for electricity, forming the basis for countless electronic devices.
MCQ
Ideal Diode
* What is the forward-bias resistance of an ideal diode?
a) Infinite (\infty)
b) Zero (0)
c) Equivalent to load resistance
d) Small but finite value
Answer: b) Zero (0)
* How does an ideal diode behave when it is forward-biased?
a) As an open circuit
b) As a voltage source
c) As a perfect insulator
d) As a short circuit (closed switch)
Answer: d) As a short circuit (closed switch)
* What is the reverse-bias resistance of an ideal diode?
a) Zero (0)
b) Small but finite value
c) Infinite (\infty)
d) Equivalent to load resistance
Answer: c) Infinite (\infty)
* How does an ideal diode behave when it is reverse-biased?
a) As a short circuit
b) As a current source
c) As a perfect conductor
d) As an open circuit (open switch)
Answer: d) As an open circuit (open switch)
* What is the knee voltage (or cut-in voltage) for an ideal diode?
a) 0.7\text{ V}
b) 0.3\text{ V}
c) **Zero (\mathbf{0}\text{ V}) **
d) Infinity (\infty)
Answer: c) Zero (\mathbf{0}\text{ V})
* In an ideal diode, the forward current is unlimited and the reverse current is:
a) Large
b) Zero (0)
c) Infinite (\infty)
d) Positive
Answer: b) Zero (0)
* The I-V characteristic curve for an ideal diode is:
a) Parabolic
b) Non-linear
c) Linear (piecewise)
d) Logarithmic
Answer: c) Linear (piecewise)
* Which of the following devices closely models the action of an ideal diode?
a) Resistor
b) Capacitor
c) Switch
d) Inductor
Answer: c) Switch
* An ideal diode conducts current in what direction?
a) Bidirectional
b) Unidirectional
c) Only reverse
d) Only when V_{in} is negative
Answer: b) Unidirectional
* When an ideal diode is forward-biased, the voltage drop across it is:
a) 0.7\text{ V}
b) \text{Battery voltage}
c) **Zero (\mathbf{0}\text{ V}) **
d) 0.3\text{ V}
Answer: c) Zero (\mathbf{0}\text{ V})
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