Semiconductor —I
Semiconductor —II
Semiconductor —III
N-Type Silicon
P-Type Silicon —I
P-Type Silicon —II
• The hole of boron atom points towards the negative terminal.
• The electron of neighboring silicon atom points toward
positive terminal.
• The electron from neighboring silicon atom falls into the
boron atom filling the hole in boron atom and creating a “new”
hole in the silicon atom.
• It appears as though a hole moves toward the negative
terminal!Diode
•A diode is a 2 lead semiconductor that acts as a one way gate to electron flow.
– Diode allows current to pass in only one direction.
•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 anode and the n-side is called cathode.
•When the anode and cathode of a pn-junction diode are connected to external voltage
such that the potential at anode is higher than the potential at cathode, the diode is said
to be forward biased.
–In a forward-biased diode current is allowed to flow through the device.
•When potential at anode is smaller than the potential at cathode, the diode is said to
be reverse biased. In a reverse-biased diode current is blocked.
Semiconductor diodes are made from semiconducting materials like silicon and germanium. There are several types of semiconductor diodes that emphasize different physical aspects or have special applications. Some of the main types are p-n junction diodes, Schottky diodes, Zener diodes, photodiodes, and light-emitting diodes (LEDs). Semiconductor diodes are widely used in electronics for rectification, voltage regulation, light emission, light detection, and other functions.
This document provides an overview of semiconductor diodes, including PN junction diodes. It discusses intrinsic and extrinsic semiconductors, doping to create N-type and P-type materials, the PN junction, depletion region and built-in voltage calculations. Forward and reverse bias characteristics are examined along with current equations. Energy band diagrams are presented for the PN junction under zero, forward and reverse bias. Other topics covered include drift and diffusion current densities, transition and diffusion capacitances, switching characteristics and breakdown mechanisms in PN junction diodes. Ratings for diodes such as maximum current and voltage are also defined.
The document discusses PN junction diodes, rectifiers, and bridge rectifiers. It begins by explaining the history and workings of PN junction diodes, including the depletion region and forward/reverse biasing. It then covers half-wave and full-wave rectifiers for converting AC to DC. Finally, it describes bridge rectifiers, including their types, working principle, advantages of higher output voltage and efficiency over center-tap rectifiers, and applications in power supplies.
This ppt is about semiconductor diodes.You can get every basic information about PN junction diode and its working and some more information about the semiconductors.
This document defines key terms related to semiconductors and diodes. It explains that semiconductors have conductivity properties between conductors and insulators. Doping adds impurities to semiconductors to increase charge carriers, which are electrons in N-type materials and holes in P-type materials. A diode has an anode and cathode, and conventional current flows from negative to positive terminals. When a diode is forward biased with positive to P-type and negative to N-type, the junction barrier is reduced and current flow is maximum.
The document discusses the operation and properties of a p-n junction diode. It describes how a p-n junction is formed at the boundary between p-type and n-type semiconductors. When forward biased, majority carriers are pushed towards the junction, lowering the barrier and allowing current to flow. When reverse biased, the depletion region widens, increasing resistance and preventing current flow. P-n junction diodes are fundamental components used in various electronic devices.
This document summarizes key concepts about semiconductor diodes:
- Diodes are electronic devices created by joining a p-type and n-type semiconductor, allowing current to flow easily in one direction. They are used for rectification in circuits.
- P-type materials have an excess of holes, making them positively charged, while N-type materials have an excess of electrons, giving them a negative charge.
- Diodes conduct current easily when forward biased by applying positive voltage to the p-side and negative to the n-side. They do not conduct in the reverse biased state.
- The Shockley diode equation models the current-voltage relationship of an ideal diode based on thermal voltage and
Semiconductor diodes are made from semiconducting materials like silicon and germanium. There are several types of semiconductor diodes that emphasize different physical aspects or have special applications. Some of the main types are p-n junction diodes, Schottky diodes, Zener diodes, photodiodes, and light-emitting diodes (LEDs). Semiconductor diodes are widely used in electronics for rectification, voltage regulation, light emission, light detection, and other functions.
This document provides an overview of semiconductor diodes, including PN junction diodes. It discusses intrinsic and extrinsic semiconductors, doping to create N-type and P-type materials, the PN junction, depletion region and built-in voltage calculations. Forward and reverse bias characteristics are examined along with current equations. Energy band diagrams are presented for the PN junction under zero, forward and reverse bias. Other topics covered include drift and diffusion current densities, transition and diffusion capacitances, switching characteristics and breakdown mechanisms in PN junction diodes. Ratings for diodes such as maximum current and voltage are also defined.
The document discusses PN junction diodes, rectifiers, and bridge rectifiers. It begins by explaining the history and workings of PN junction diodes, including the depletion region and forward/reverse biasing. It then covers half-wave and full-wave rectifiers for converting AC to DC. Finally, it describes bridge rectifiers, including their types, working principle, advantages of higher output voltage and efficiency over center-tap rectifiers, and applications in power supplies.
This ppt is about semiconductor diodes.You can get every basic information about PN junction diode and its working and some more information about the semiconductors.
This document defines key terms related to semiconductors and diodes. It explains that semiconductors have conductivity properties between conductors and insulators. Doping adds impurities to semiconductors to increase charge carriers, which are electrons in N-type materials and holes in P-type materials. A diode has an anode and cathode, and conventional current flows from negative to positive terminals. When a diode is forward biased with positive to P-type and negative to N-type, the junction barrier is reduced and current flow is maximum.
The document discusses the operation and properties of a p-n junction diode. It describes how a p-n junction is formed at the boundary between p-type and n-type semiconductors. When forward biased, majority carriers are pushed towards the junction, lowering the barrier and allowing current to flow. When reverse biased, the depletion region widens, increasing resistance and preventing current flow. P-n junction diodes are fundamental components used in various electronic devices.
This document summarizes key concepts about semiconductor diodes:
- Diodes are electronic devices created by joining a p-type and n-type semiconductor, allowing current to flow easily in one direction. They are used for rectification in circuits.
- P-type materials have an excess of holes, making them positively charged, while N-type materials have an excess of electrons, giving them a negative charge.
- Diodes conduct current easily when forward biased by applying positive voltage to the p-side and negative to the n-side. They do not conduct in the reverse biased state.
- The Shockley diode equation models the current-voltage relationship of an ideal diode based on thermal voltage and
The document discusses diodes, including their history and components. It describes how a diode is constructed from a P-type and N-type semiconductor material, forming a PN junction. At the junction, electrons diffuse into holes, creating a depletion region that acts as an insulator under reverse bias but allows current to flow under forward bias. The document outlines diode applications such as rectification in power supplies and their characteristic I-V curve.
This document describes semiconductors and diodes. It defines semiconductors as materials that conduct electricity better than insulators but not as well as conductors. N-type and P-type semiconductors are described based on adding impurities that add free electrons or holes. A diode consists of a P-N junction where current can only flow in one direction. Diodes can be used as rectifiers to convert alternating current to direct current in either half-wave or full-wave configurations. A capacitor can be used to smooth the rectified output voltage and current.
The document summarizes different types of semiconductor diodes. It discusses the theory of p-n junctions and how a p-n junction forms a diode. It describes the ideal behavior of a diode under forward and reverse bias. The characteristics of a diode are shown in its volt-current curve. Different types of diodes are described briefly, including Zener diodes, light emitting diodes, photo diodes, and their uses.
Pn junction diode class 12 investegatory projectabhijeet singh
The document is a physics investigatory project report on P-N junction diodes submitted by Abhijeet Kumar Singh of class XII. It includes an acknowledgment section thanking various people for their support and guidance. The content sections cover diode theory, zero bias, reverse bias, forward bias, breakdown region, useful diode parameters and ideal versus real junction diode characteristics. Diagrams are included to illustrate the concepts. References and websites used for the project are listed at the end.
Semiconductor Diode :
What is Semiconductor Diode?
How is it Work?
What are the Types?
Current Flow in Forward And Reverse Bios?
What is Light Emitting Diode (LED)?
What is Zener Diode?
and in aditional :
P-N Junction and its formation
Formation of Depletion Layer
External Biasing of P-N Junction
V-I Characteristics of P-N Junction
Zener Breakdown
Avalanche Breakdown
Comparison between Zener and Avalanche Breakdown
This document summarizes key topics related to electronics devices and circuits, including:
1) The operation and characteristics of unbiased, forward biased, and reverse biased diodes. Forward biasing reduces the depletion region and allows current to flow, while reverse biasing increases the depletion region and prevents current.
2) Breakdown mechanisms including avalanche and Zener effects which allow current to flow under high reverse voltages.
3) Energy bands and levels that describe the quantum mechanical states of electrons in materials, and how semiconductor materials have a forbidden gap between valence and conduction bands.
4) How the barrier potential of a p-n junction decreases with increasing temperature, allowing more current to flow.
A PN junction is formed by joining a P-type semiconductor with an N-type semiconductor. When joined, a depletion layer forms at the junction that acts as an insulator. When forward biased, current flows easily through the junction. When reverse biased, very little current flows due to the high resistance of the depletion layer acting as a barrier. PN junction diodes are used as rectifiers, switches, detectors, and light emitting diodes (LEDs) in electronic circuits.
This document contains 40 electronics viva questions and their answers related to topics like electronic components, semiconductors, diodes, PN junctions, biasing, rectifiers, transformers, and logic gates. Some key points covered are:
- Electronics deals with controlling electron flow using electrical devices, while engineering applies science to benefit humanity.
- Diodes allow current to flow in one direction, with types including small signal, rectifier, switching, Zener, and LEDs.
- Semiconductors partially conduct electricity, with major roles played by PN junction diodes and Zener diodes.
- Biasing a PN junction connects it to an external voltage, with
This document discusses semiconductor diodes and rectifiers. It begins by explaining the physical principles of semiconductors, including intrinsic semiconductors and how doping with materials like phosphorus or boron creates n-type and p-type semiconductors. When a p-type and n-type material meet, it forms a pn junction with interesting electrical properties. Diodes are made from pn junctions and exhibit asymmetric conduction, allowing current in one direction but blocking it in the other. Diode circuits and models are also covered, along with important applications like rectification where diodes are used to convert AC to DC power.
LEDs (light-emitting diodes) are semiconductor devices that emit light when activated. They work by passing electricity through two opposing materials (p-type and n-type semiconductor), causing electrons to recombine with electron holes and release energy in the form of photons. Common applications of LEDs include indicator lights, displays, traffic lights and signs, lighting (replacing incandescent bulbs), and backlighting for LCDs.
There are several major types of diodes: Zener diodes maintain a constant voltage in reverse bias within a range of currents. Varactor diodes have a capacitance that varies inversely with reverse voltage. Light-emitting diodes (LEDs) emit light when forward-biased and are used for displays, lights, and more. Photodiodes exhibit increasing reverse current with light intensity and are used to detect light. Laser diodes produce coherent monochromatic light through stimulated emission and are used in printers, fiber optics, and medicine. Schottky diodes are used in high-frequency applications. PIN diodes act as capacitors when reverse-biased and variable resistors when forward-biased. Tunnel diodes
This document summarizes different types of PN diodes. It begins by explaining the theory of a PN junction, how a PN junction forms a diode, and the ideal characteristics of a diode. It then discusses the volt-current characteristics and biasing of diodes. The rest of the document describes several specific types of diodes - Zener diodes, light emitting diodes, photo diodes, and tunnel diodes. It provides details on their construction, operating principles, and common applications.
This document discusses semiconductors and semiconductor diodes. It defines semiconductors and describes their properties. It explains how doping semiconductors creates an excess of either electrons or holes, resulting in n-type or p-type materials. It then discusses how a p-n junction diode works, including the formation of a depletion region and the forward and reverse bias connections. The document also covers how diodes can be used for rectification of alternating current into direct current, including half-wave and full-wave rectification, and how a capacitor can smooth the rectified output.
The document discusses semiconductor diodes and their history. It explains that semiconductors like silicon proved to be smaller, lighter, and more reliable replacements for vacuum tubes in electronics. The document then covers key topics like silicon crystals, energy band concepts, doping to create N-type and P-type semiconductors, PN junctions, biasing of diodes, and breakdown mechanisms. Specific diode types like LEDs and photodiodes are also summarized.
A PN junction diode allows current to flow in one direction. It is formed by joining a P-type semiconductor with an N-type semiconductor. Current can be made to flow by applying either forward or reverse bias. In forward bias, the P region is connected to the positive terminal and the N region to the negative terminal. In reverse bias, the connections are reversed. The depletion region where there are no free charges forms across the PN junction. Breakdown can occur due to Zener or avalanche effects at high reverse voltages. Special diodes include Zener diodes, which have a controlled reverse breakdown voltage, and photo diodes, which generate a current when exposed to light.
1) A PN junction diode allows large numbers of electrons and holes to flow under forward bias when the depletion region collapses. Under reverse bias, it acts as an open switch that blocks most carrier flow.
2) When a PN junction forms, electrons diffuse from the N to P region, leaving positive ions in the N region and negative ions in the P region. This forms the depletion region that sets up an electric field.
3) A diode's V-I characteristic shows large forward current above the knee voltage but small reverse saturation current below the breakdown voltage, with the ideal diode approximated as a closed switch above and open below the knee voltage.
This document presents an agenda for a lecture on diodes. It will introduce basic diode concepts like their composition and circuit models. It will discuss applications of diodes in circuits and different types of diodes like Zener diodes and light emitting diodes. The lecture will show real diode components and their usage. It will conclude with a summary of diodes and thank sources in a bibliography.
The document discusses PN junction diodes and their applications. It describes how a PN junction forms and its electrical characteristics. Different types of diodes are covered, including Zener diodes and light emitting diodes. Circuit applications of diodes such as rectification, voltage regulation, and signal processing are explained through examples. Key diode properties like forward and reverse biasing, turn-on voltage, and dynamic resistance are defined. Diode models from ideal to linear element are also introduced.
A semiconductor diode allows current to flow in only one direction by taking advantage of the junction between n-type and p-type semiconductors. When forward biased, majority carriers can flow across the junction. When reversed biased, the depletion layer widens, blocking current. Diodes can be used as rectifiers to convert alternating current into pulsing direct current through half-wave or smooth direct current through full-wave rectification. A capacitor added to the output smoothes the pulsating direct current into a steady direct current voltage.
This document provides an overview of semiconductors and diodes. It discusses how semiconductors conduct electricity through the movement of electrons and holes. It describes intrinsic and extrinsic conduction in semiconductors and how doping with elements like boron and phosphorus creates p-type and n-type materials. The document explains how a PN junction forms a diode and how diodes can be forward or reverse biased to control current flow. It provides details on rectifier diodes, signal diodes, LEDs, and zener diodes.
This document provides an introduction to semiconductors. It discusses how semiconductors can behave as either conductors or insulators depending on doping, and describes the crystal lattice structure of semiconductors. It also explains intrinsic and extrinsic semiconductors, detailing how doping with trivalent or pentavalent impurities creates N-type or P-type materials respectively. The document concludes by discussing diode operation under forward and reverse bias conditions.
The document discusses diodes, including their history and components. It describes how a diode is constructed from a P-type and N-type semiconductor material, forming a PN junction. At the junction, electrons diffuse into holes, creating a depletion region that acts as an insulator under reverse bias but allows current to flow under forward bias. The document outlines diode applications such as rectification in power supplies and their characteristic I-V curve.
This document describes semiconductors and diodes. It defines semiconductors as materials that conduct electricity better than insulators but not as well as conductors. N-type and P-type semiconductors are described based on adding impurities that add free electrons or holes. A diode consists of a P-N junction where current can only flow in one direction. Diodes can be used as rectifiers to convert alternating current to direct current in either half-wave or full-wave configurations. A capacitor can be used to smooth the rectified output voltage and current.
The document summarizes different types of semiconductor diodes. It discusses the theory of p-n junctions and how a p-n junction forms a diode. It describes the ideal behavior of a diode under forward and reverse bias. The characteristics of a diode are shown in its volt-current curve. Different types of diodes are described briefly, including Zener diodes, light emitting diodes, photo diodes, and their uses.
Pn junction diode class 12 investegatory projectabhijeet singh
The document is a physics investigatory project report on P-N junction diodes submitted by Abhijeet Kumar Singh of class XII. It includes an acknowledgment section thanking various people for their support and guidance. The content sections cover diode theory, zero bias, reverse bias, forward bias, breakdown region, useful diode parameters and ideal versus real junction diode characteristics. Diagrams are included to illustrate the concepts. References and websites used for the project are listed at the end.
Semiconductor Diode :
What is Semiconductor Diode?
How is it Work?
What are the Types?
Current Flow in Forward And Reverse Bios?
What is Light Emitting Diode (LED)?
What is Zener Diode?
and in aditional :
P-N Junction and its formation
Formation of Depletion Layer
External Biasing of P-N Junction
V-I Characteristics of P-N Junction
Zener Breakdown
Avalanche Breakdown
Comparison between Zener and Avalanche Breakdown
This document summarizes key topics related to electronics devices and circuits, including:
1) The operation and characteristics of unbiased, forward biased, and reverse biased diodes. Forward biasing reduces the depletion region and allows current to flow, while reverse biasing increases the depletion region and prevents current.
2) Breakdown mechanisms including avalanche and Zener effects which allow current to flow under high reverse voltages.
3) Energy bands and levels that describe the quantum mechanical states of electrons in materials, and how semiconductor materials have a forbidden gap between valence and conduction bands.
4) How the barrier potential of a p-n junction decreases with increasing temperature, allowing more current to flow.
A PN junction is formed by joining a P-type semiconductor with an N-type semiconductor. When joined, a depletion layer forms at the junction that acts as an insulator. When forward biased, current flows easily through the junction. When reverse biased, very little current flows due to the high resistance of the depletion layer acting as a barrier. PN junction diodes are used as rectifiers, switches, detectors, and light emitting diodes (LEDs) in electronic circuits.
This document contains 40 electronics viva questions and their answers related to topics like electronic components, semiconductors, diodes, PN junctions, biasing, rectifiers, transformers, and logic gates. Some key points covered are:
- Electronics deals with controlling electron flow using electrical devices, while engineering applies science to benefit humanity.
- Diodes allow current to flow in one direction, with types including small signal, rectifier, switching, Zener, and LEDs.
- Semiconductors partially conduct electricity, with major roles played by PN junction diodes and Zener diodes.
- Biasing a PN junction connects it to an external voltage, with
This document discusses semiconductor diodes and rectifiers. It begins by explaining the physical principles of semiconductors, including intrinsic semiconductors and how doping with materials like phosphorus or boron creates n-type and p-type semiconductors. When a p-type and n-type material meet, it forms a pn junction with interesting electrical properties. Diodes are made from pn junctions and exhibit asymmetric conduction, allowing current in one direction but blocking it in the other. Diode circuits and models are also covered, along with important applications like rectification where diodes are used to convert AC to DC power.
LEDs (light-emitting diodes) are semiconductor devices that emit light when activated. They work by passing electricity through two opposing materials (p-type and n-type semiconductor), causing electrons to recombine with electron holes and release energy in the form of photons. Common applications of LEDs include indicator lights, displays, traffic lights and signs, lighting (replacing incandescent bulbs), and backlighting for LCDs.
There are several major types of diodes: Zener diodes maintain a constant voltage in reverse bias within a range of currents. Varactor diodes have a capacitance that varies inversely with reverse voltage. Light-emitting diodes (LEDs) emit light when forward-biased and are used for displays, lights, and more. Photodiodes exhibit increasing reverse current with light intensity and are used to detect light. Laser diodes produce coherent monochromatic light through stimulated emission and are used in printers, fiber optics, and medicine. Schottky diodes are used in high-frequency applications. PIN diodes act as capacitors when reverse-biased and variable resistors when forward-biased. Tunnel diodes
This document summarizes different types of PN diodes. It begins by explaining the theory of a PN junction, how a PN junction forms a diode, and the ideal characteristics of a diode. It then discusses the volt-current characteristics and biasing of diodes. The rest of the document describes several specific types of diodes - Zener diodes, light emitting diodes, photo diodes, and tunnel diodes. It provides details on their construction, operating principles, and common applications.
This document discusses semiconductors and semiconductor diodes. It defines semiconductors and describes their properties. It explains how doping semiconductors creates an excess of either electrons or holes, resulting in n-type or p-type materials. It then discusses how a p-n junction diode works, including the formation of a depletion region and the forward and reverse bias connections. The document also covers how diodes can be used for rectification of alternating current into direct current, including half-wave and full-wave rectification, and how a capacitor can smooth the rectified output.
The document discusses semiconductor diodes and their history. It explains that semiconductors like silicon proved to be smaller, lighter, and more reliable replacements for vacuum tubes in electronics. The document then covers key topics like silicon crystals, energy band concepts, doping to create N-type and P-type semiconductors, PN junctions, biasing of diodes, and breakdown mechanisms. Specific diode types like LEDs and photodiodes are also summarized.
A PN junction diode allows current to flow in one direction. It is formed by joining a P-type semiconductor with an N-type semiconductor. Current can be made to flow by applying either forward or reverse bias. In forward bias, the P region is connected to the positive terminal and the N region to the negative terminal. In reverse bias, the connections are reversed. The depletion region where there are no free charges forms across the PN junction. Breakdown can occur due to Zener or avalanche effects at high reverse voltages. Special diodes include Zener diodes, which have a controlled reverse breakdown voltage, and photo diodes, which generate a current when exposed to light.
1) A PN junction diode allows large numbers of electrons and holes to flow under forward bias when the depletion region collapses. Under reverse bias, it acts as an open switch that blocks most carrier flow.
2) When a PN junction forms, electrons diffuse from the N to P region, leaving positive ions in the N region and negative ions in the P region. This forms the depletion region that sets up an electric field.
3) A diode's V-I characteristic shows large forward current above the knee voltage but small reverse saturation current below the breakdown voltage, with the ideal diode approximated as a closed switch above and open below the knee voltage.
This document presents an agenda for a lecture on diodes. It will introduce basic diode concepts like their composition and circuit models. It will discuss applications of diodes in circuits and different types of diodes like Zener diodes and light emitting diodes. The lecture will show real diode components and their usage. It will conclude with a summary of diodes and thank sources in a bibliography.
The document discusses PN junction diodes and their applications. It describes how a PN junction forms and its electrical characteristics. Different types of diodes are covered, including Zener diodes and light emitting diodes. Circuit applications of diodes such as rectification, voltage regulation, and signal processing are explained through examples. Key diode properties like forward and reverse biasing, turn-on voltage, and dynamic resistance are defined. Diode models from ideal to linear element are also introduced.
A semiconductor diode allows current to flow in only one direction by taking advantage of the junction between n-type and p-type semiconductors. When forward biased, majority carriers can flow across the junction. When reversed biased, the depletion layer widens, blocking current. Diodes can be used as rectifiers to convert alternating current into pulsing direct current through half-wave or smooth direct current through full-wave rectification. A capacitor added to the output smoothes the pulsating direct current into a steady direct current voltage.
This document provides an overview of semiconductors and diodes. It discusses how semiconductors conduct electricity through the movement of electrons and holes. It describes intrinsic and extrinsic conduction in semiconductors and how doping with elements like boron and phosphorus creates p-type and n-type materials. The document explains how a PN junction forms a diode and how diodes can be forward or reverse biased to control current flow. It provides details on rectifier diodes, signal diodes, LEDs, and zener diodes.
This document provides an introduction to semiconductors. It discusses how semiconductors can behave as either conductors or insulators depending on doping, and describes the crystal lattice structure of semiconductors. It also explains intrinsic and extrinsic semiconductors, detailing how doping with trivalent or pentavalent impurities creates N-type or P-type materials respectively. The document concludes by discussing diode operation under forward and reverse bias conditions.
The document discusses semiconductor diodes and their applications. It describes the P-N junction diode, how it allows current to flow in only one direction. A bridge rectifier circuit uses 4 diodes in a bridge configuration to convert alternating current to pulsating direct current. Filter circuits such as 'T' and 'π' filters can be used to create smoother direct current output from the rectified signal. The document also discusses zener diodes and how they can be used as voltage regulators.
The document discusses several topics related to electromechanics and semiconductor devices:
1) It defines electromechanics as dealing with mechanical forces in electric circuits, and provides examples of common electromechanical devices like household appliances.
2) It explains rectification as the process of converting alternating current to direct current using diodes, and describes the basic operation and differences between half-wave and full-wave rectifier circuits.
3) It discusses semiconductors, describing their properties and how intrinsic and extrinsic semiconductors are formed by doping with impurities, and how a PN junction is formed between a P-type and N-type semiconductor to create a diode.
This document discusses semiconductor materials and devices. It begins by explaining electricity and electron bands in atoms. It then discusses the properties and atomic structures of conductors, insulators, and semiconductors. Semiconductors can be made to act as insulators or conductors through doping, which introduces impurity atoms. The document describes how n-type and p-type semiconductors are formed and their current flow. It concludes by explaining how a p-n junction diode is formed at the interface of p-type and n-type semiconductors and its current-voltage characteristics.
- The document discusses semiconductors and PN junction diodes. It covers topics like atomic structure of semiconductors, conduction in semiconductors, N-type and P-type semiconductors, the PN junction, forward and reverse biasing of the PN junction, and applications of PN junction diodes.
- A key point is that a PN junction diode allows current to flow easily in one direction but blocks it in the reverse direction. This is achieved by doping one side of silicon with an N-type dopant and the other side with a P-type dopant.
- Under forward bias, the voltage drop across the diode occurs due to
This document outlines the course objectives, outcomes, contents, and units for a Basic Electronics course at Matrusri Engineering College. The course aims to teach students about the characteristics, design concepts, and applications of diodes, transistors, feedback amplifiers, oscillators, and operational amplifiers. Specific topics covered include rectifier and regulator circuits, biasing of BJTs and FETs, oscillator design, logic gates, and data acquisition systems. One unit focuses on semiconductor materials and diode circuit design, while another covers Zener diodes, voltage regulators, and the construction and applications of cathode ray tubes in oscilloscopes.
Electrical current, voltage, resistance, capacitance, and inductance are a few of the basic elements of electronics and radio. Apart from current, voltage, resistance, capacitance, and inductance, there are many other interesting elements to electronic technology. ... Use Electronics Notes to learn electronics online.
The document discusses a course on basic electronics at Matrusri Engineering College. It includes:
1. The course objectives are to understand the characteristics and design concepts of diodes, transistors, feedback amplifiers, oscillators, and operational amplifiers.
2. The course outcomes are for students to be able to analyze and design rectifier, regulator, amplifier, and oscillator circuits and understand the performance of transistors.
3. The first module will cover the characteristics of PN junctions, including half wave and full wave rectifiers, and diodes such as Zener diodes.
This document discusses semiconductor diodes and their properties. It begins by explaining that semiconductors have conductivity between conductors and insulators. Their conductivity increases with temperature as electrons break free from atoms. There are two types of semiconductors - p-type and n-type - which are created through doping with different impurities. A semiconductor diode consists of a p-n junction where a p-type and n-type material meet. It allows current to flow in one direction when forward-biased but blocks it when reverse-biased, enabling its use as a rectifier.
This document provides an overview of semiconductor and diode theory. It discusses how semiconductors like silicon are doped to create excess electrons (n-type) or holes (p-type). When a p-type and n-type semiconductor are joined, a pn junction is formed with a depletion region that acts as an insulator. Forward biasing the junction collapses the depletion region, allowing current to flow. Reverse bias widens the depletion region, preventing current flow. The junction forms a potential barrier of around 0.7V that electrons must overcome to diffuse across.
This document provides an overview of semiconductor and diode theory. It discusses how semiconductors like silicon are doped to create excess electrons (n-type) or holes (p-type). When a p-type and n-type semiconductor are joined, a pn junction is formed with a depletion region that acts as an insulator. Forward biasing the junction collapses the depletion region, allowing current to flow. Reverse bias widens the depletion region, preventing current flow. The junction forms a potential barrier of around 0.7V that electrons must overcome to diffuse across.
Semiconductor materials like silicon can be used as either conductors or insulators depending on doping. Doping involves adding small amounts of other elements to the semiconductor crystal lattice which provides extra electrons (n-type) or electron vacancies called holes (p-type). The type and amount of doping determines whether the semiconductor acts as a good conductor with low resistance and easy electron flow, or as an insulator with high resistance that suppresses current.
The document discusses semiconductor devices and their characteristics. It covers topics like energy bands in semiconductors, carrier concentration, drift and diffusion current, the Hall effect, and PN junction diodes. Specifically, it describes direct and indirect bandgap semiconductors, how carrier concentration is determined in intrinsic and extrinsic semiconductors, and how drift current occurs under an applied electric field while diffusion current moves charges from high to low concentration regions. It also explains the Hall effect where a voltage develops perpendicular to the current and magnetic field.
Semiconductor fundamentals can be summarized as follows:
1) Conductors, insulators, and semiconductors differ in their ability to conduct electricity based on their energy band structure and band gap. Conductors have overlapping or partially filled bands allowing electron flow, insulators have a large band gap suppressing flow, and semiconductors have a small band gap allowing some flow.
2) Intrinsic semiconductors like silicon are pure, while extrinsic semiconductors are doped with impurities to create excess electrons (n-type) or holes (p-type) improving conductivity.
3) A pn junction diode allows current in one direction by forward biasing the junction
This document summarizes the key characteristics and properties of a p-n junction diode. It discusses:
1) The basic structure of a p-n junction diode consisting of p-type and n-type semiconductor materials.
2) The operation of a diode under reverse and forward bias conditions, including the formation of a depletion region and how it affects carrier flow.
3) The current-voltage characteristics of a diode and how the current changes exponentially with forward voltage but remains low in reverse bias.
4) Important diode parameters like the reverse saturation current, thermal voltage, and their relationship to the diode current equation.
1. The document discusses the atomic structure of semiconductors and how doping creates an excess or deficiency of electrons or holes, turning silicon into an n-type or p-type semiconductor.
2. When a p-type and n-type semiconductor are joined, electrons from the n-side diffuse into the p-side and holes from the p-side diffuse into the n-side, leaving an area devoid of charge carriers called the depletion region.
3. A p-n junction diode allows current to flow easily in one direction when forward biased but strongly restricts it in the reverse direction, demonstrated by its characteristic I-V curve.
Majority and minority charge carriers are defined for p-type and n-type semiconductors. In p-type semiconductors, holes are the majority carriers while electrons are the minority carriers. In n-type semiconductors, electrons are the majority carriers and holes are the minority carriers. Semiconductors are doped with impurities to increase the number of majority carriers, making the material either p-type or n-type. A depletion region forms at the PN junction where majority carriers diffuse across and recombine, leaving an area devoid of carriers.
The document discusses various components used in rectification circuits, including thermionic valves, semiconductors, transistors, rectifiers, transformers, and choke coils. It provides details on their construction and working principles. The key components and processes discussed are diode valves and their use in half-wave rectification of alternating current to direct current.
Diodes are the simplest semiconductor devices and are two-terminal components that allow current to flow easily in one direction but restrict it in the other. They exhibit nearly zero voltage drop when conducting and behave as an open circuit when not conducting. The electrical characteristics of silicon and germanium can be improved through doping with materials that introduce free electrons or holes, creating n-type or p-type semiconductors. When a p-type and n-type material are joined, a p-n junction forms with distinct conduction and non-conduction regions that enable the diode's rectifying behavior.
Home security is of paramount importance in today's world, where we rely more on technology, home
security is crucial. Using technology to make homes safer and easier to control from anywhere is
important. Home security is important for the occupant’s safety. In this paper, we came up with a low cost,
AI based model home security system. The system has a user-friendly interface, allowing users to start
model training and face detection with simple keyboard commands. Our goal is to introduce an innovative
home security system using facial recognition technology. Unlike traditional systems, this system trains
and saves images of friends and family members. The system scans this folder to recognize familiar faces
and provides real-time monitoring. If an unfamiliar face is detected, it promptly sends an email alert,
ensuring a proactive response to potential security threats.
Blood finder application project report (1).pdfKamal Acharya
Blood Finder is an emergency time app where a user can search for the blood banks as
well as the registered blood donors around Mumbai. This application also provide an
opportunity for the user of this application to become a registered donor for this user have
to enroll for the donor request from the application itself. If the admin wish to make user
a registered donor, with some of the formalities with the organization it can be done.
Specialization of this application is that the user will not have to register on sign-in for
searching the blood banks and blood donors it can be just done by installing the
application to the mobile.
The purpose of making this application is to save the user’s time for searching blood of
needed blood group during the time of the emergency.
This is an android application developed in Java and XML with the connectivity of
SQLite database. This application will provide most of basic functionality required for an
emergency time application. All the details of Blood banks and Blood donors are stored
in the database i.e. SQLite.
This application allowed the user to get all the information regarding blood banks and
blood donors such as Name, Number, Address, Blood Group, rather than searching it on
the different websites and wasting the precious time. This application is effective and
user friendly.
Height and depth gauge linear metrology.pdfq30122000
Height gauges may also be used to measure the height of an object by using the underside of the scriber as the datum. The datum may be permanently fixed or the height gauge may have provision to adjust the scale, this is done by sliding the scale vertically along the body of the height gauge by turning a fine feed screw at the top of the gauge; then with the scriber set to the same level as the base, the scale can be matched to it. This adjustment allows different scribers or probes to be used, as well as adjusting for any errors in a damaged or resharpened probe.
Discover the latest insights on Data Driven Maintenance with our comprehensive webinar presentation. Learn about traditional maintenance challenges, the right approach to utilizing data, and the benefits of adopting a Data Driven Maintenance strategy. Explore real-world examples, industry best practices, and innovative solutions like FMECA and the D3M model. This presentation, led by expert Jules Oudmans, is essential for asset owners looking to optimize their maintenance processes and leverage digital technologies for improved efficiency and performance. Download now to stay ahead in the evolving maintenance landscape.
Software Engineering and Project Management - Introduction, Modeling Concepts...Prakhyath Rai
Introduction, Modeling Concepts and Class Modeling: What is Object orientation? What is OO development? OO Themes; Evidence for usefulness of OO development; OO modeling history. Modeling
as Design technique: Modeling, abstraction, The Three models. Class Modeling: Object and Class Concept, Link and associations concepts, Generalization and Inheritance, A sample class model, Navigation of class models, and UML diagrams
Building the Analysis Models: Requirement Analysis, Analysis Model Approaches, Data modeling Concepts, Object Oriented Analysis, Scenario-Based Modeling, Flow-Oriented Modeling, class Based Modeling, Creating a Behavioral Model.
Null Bangalore | Pentesters Approach to AWS IAMDivyanshu
#Abstract:
- Learn more about the real-world methods for auditing AWS IAM (Identity and Access Management) as a pentester. So let us proceed with a brief discussion of IAM as well as some typical misconfigurations and their potential exploits in order to reinforce the understanding of IAM security best practices.
- Gain actionable insights into AWS IAM policies and roles, using hands on approach.
#Prerequisites:
- Basic understanding of AWS services and architecture
- Familiarity with cloud security concepts
- Experience using the AWS Management Console or AWS CLI.
- For hands on lab create account on [killercoda.com](https://killercoda.com/cloudsecurity-scenario/)
# Scenario Covered:
- Basics of IAM in AWS
- Implementing IAM Policies with Least Privilege to Manage S3 Bucket
- Objective: Create an S3 bucket with least privilege IAM policy and validate access.
- Steps:
- Create S3 bucket.
- Attach least privilege policy to IAM user.
- Validate access.
- Exploiting IAM PassRole Misconfiguration
-Allows a user to pass a specific IAM role to an AWS service (ec2), typically used for service access delegation. Then exploit PassRole Misconfiguration granting unauthorized access to sensitive resources.
- Objective: Demonstrate how a PassRole misconfiguration can grant unauthorized access.
- Steps:
- Allow user to pass IAM role to EC2.
- Exploit misconfiguration for unauthorized access.
- Access sensitive resources.
- Exploiting IAM AssumeRole Misconfiguration with Overly Permissive Role
- An overly permissive IAM role configuration can lead to privilege escalation by creating a role with administrative privileges and allow a user to assume this role.
- Objective: Show how overly permissive IAM roles can lead to privilege escalation.
- Steps:
- Create role with administrative privileges.
- Allow user to assume the role.
- Perform administrative actions.
- Differentiation between PassRole vs AssumeRole
Try at [killercoda.com](https://killercoda.com/cloudsecurity-scenario/)
Mechatronics is a multidisciplinary field that refers to the skill sets needed in the contemporary, advanced automated manufacturing industry. At the intersection of mechanics, electronics, and computing, mechatronics specialists create simpler, smarter systems. Mechatronics is an essential foundation for the expected growth in automation and manufacturing.
Mechatronics deals with robotics, control systems, and electro-mechanical systems.
Digital Twins Computer Networking Paper Presentation.pptxaryanpankaj78
A Digital Twin in computer networking is a virtual representation of a physical network, used to simulate, analyze, and optimize network performance and reliability. It leverages real-time data to enhance network management, predict issues, and improve decision-making processes.
DEEP LEARNING FOR SMART GRID INTRUSION DETECTION: A HYBRID CNN-LSTM-BASED MODELijaia
As digital technology becomes more deeply embedded in power systems, protecting the communication
networks of Smart Grids (SG) has emerged as a critical concern. Distributed Network Protocol 3 (DNP3)
represents a multi-tiered application layer protocol extensively utilized in Supervisory Control and Data
Acquisition (SCADA)-based smart grids to facilitate real-time data gathering and control functionalities.
Robust Intrusion Detection Systems (IDS) are necessary for early threat detection and mitigation because
of the interconnection of these networks, which makes them vulnerable to a variety of cyberattacks. To
solve this issue, this paper develops a hybrid Deep Learning (DL) model specifically designed for intrusion
detection in smart grids. The proposed approach is a combination of the Convolutional Neural Network
(CNN) and the Long-Short-Term Memory algorithms (LSTM). We employed a recent intrusion detection
dataset (DNP3), which focuses on unauthorized commands and Denial of Service (DoS) cyberattacks, to
train and test our model. The results of our experiments show that our CNN-LSTM method is much better
at finding smart grid intrusions than other deep learning algorithms used for classification. In addition,
our proposed approach improves accuracy, precision, recall, and F1 score, achieving a high detection
accuracy rate of 99.50%.
Accident detection system project report.pdfKamal Acharya
The Rapid growth of technology and infrastructure has made our lives easier. The
advent of technology has also increased the traffic hazards and the road accidents take place
frequently which causes huge loss of life and property because of the poor emergency facilities.
Many lives could have been saved if emergency service could get accident information and
reach in time. Our project will provide an optimum solution to this draw back. A piezo electric
sensor can be used as a crash or rollover detector of the vehicle during and after a crash. With
signals from a piezo electric sensor, a severe accident can be recognized. According to this
project when a vehicle meets with an accident immediately piezo electric sensor will detect the
signal or if a car rolls over. Then with the help of GSM module and GPS module, the location
will be sent to the emergency contact. Then after conforming the location necessary action will
be taken. If the person meets with a small accident or if there is no serious threat to anyone’s
life, then the alert message can be terminated by the driver by a switch provided in order to
avoid wasting the valuable time of the medical rescue team.
2. Semiconductor —I
• Materials that permit flow of electrons are called
conductors (e.g., gold, silver, copper, etc.).
• Materials that block flow of electrons are called
insulators (e.g., rubber, glass, Teflon, mica, etc.).
• Materials whose conductivity falls between those
of conductors and insulators are called
semiconductors.
• Semiconductors are “part-time” conductors
whose conductivity can be controlled.
germanium
Semiconductors
silicon
3. Semiconductor —II
• Silicon is the most common material used to build semiconductor devices.
• Si is the main ingredient of sand and it is estimated that a cubic mile of seawater
contains 15,000 tons of Si.
• Si is spun and grown into a crystalline structure and cut into wafers to make
electronic devices.
4. Semiconductor —III
• Atoms in a pure silicon wafer contains four electrons in outer orbit (called valence
electrons).
– Germanium is another semiconductor material with four valence electrons.
• In the crystalline lattice structure of Si, the valence electrons of every Si atom are
locked up in covalent bonds with the valence electrons of four neighboring Si atoms.
– In pure form, Si wafer does not contain any free charge carriers.
– An applied voltage across pure Si wafer does not yield electron flow through the wafer.
– A pure Si wafer is said to act as an insulator.
• In order to make useful semiconductor devices, materials such as phosphorus (P) and
boron (B) are added to Si to change Si’s conductivity.
4 valence electrons
5. N-Type Silicon
• Pentavalent impurities such as phosphorus, arsenic, antimony, and bismuth have 5
valence electrons.
• When phosphorus impurity is added to Si, every phosphorus atom’s four valence
electrons are locked up in covalent bond with valence electrons of four neighboring
Si atoms. However, the 5th valence electron of phosphorus atom does not find a
binding electron and thus remains free to float. When a voltage is applied across the
silicon-phosphorus mixture, free electrons migrate toward the positive voltage end.
• When phosphorus is added to Si to yield the above effect, we say that Si is doped
with phosphorus. The resulting mixture is called N-type silicon (N: negative charge
carrier silicon).
• The pentavalent impurities are referred to as donor impurities.
5 valence electrons
6. P-Type Silicon —I
• Trivalent impurities e.g., boron, aluminum, indium, and gallium have 3 valence
electrons.
• When boron is added to Si, every boron atom’s three valence electrons are locked up
in covalent bond with valence electrons of three neighboring Si atoms. However, a
vacant spot “hole” is created within the covalent bond between one boron atom and
a neighboring Si atom. The holes are considered to be positive charge carriers.
When a voltage is applied across the silicon-boron mixture, a hole moves toward the
negative voltage end while a neighboring electron fills in its place.
• When boron is added to Si to yield the above effect, we say that Si is doped with
boron. The resulting mixture is called P-type silicon (P: positive charge carrier
silicon).
• The trivalent impurities are referred to as acceptor impurities.
3 valence electrons
7. P-Type Silicon —II
• The hole of boron atom points towards the negative terminal.
• The electron of neighboring silicon atom points toward
positive terminal.
• The electron from neighboring silicon atom falls into the
boron atom filling the hole in boron atom and creating a “new”
hole in the silicon atom.
• It appears as though a hole moves toward the negative
terminal!
8. Diode
•A diode is a 2 lead semiconductor that acts as a one way gate to electron flow.
– Diode allows current to pass in only one direction.
•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 anode and the n-side is called cathode.
•When the anode and cathode of a pn-junction diode are connected to external voltage
such that the potential at anode is higher than the potential at cathode, the diode is said
to be forward biased.
–In a forward-biased diode current is allowed to flow through the device.
•When potential at anode is smaller than the potential at cathode, the diode is said to
be reverse biased. In a reverse-biased diode current is blocked.
+ - + -
9. Water Analogy of Diodes
• When water pressure on left overcomes the restoring force of spring, the gate is
opened and water is allowed to flow .
• When water pressure is from right to left, the gate is pressed against the solid stop
and no water is allowed to flow.
• Spring restoring force is analogous to 0.6V needed to forward bias a Si diode.
10. Diode: How it Works —I
• When a diode is
connected to a battery as
shown, electrons from
the n-side and holes from
the p-side are forced
toward the center by the
electrical field supplied
by the battery. The
electrons and holes
combine causing the
current to pass through
the diode. When a diode
is arranged in this way, it
is said to be forward-
biased.
Forward-biased (“open door”)
Repels holes
Repels electrons
11. Diode: How it Works—II
• A diode’s one-way gate feature does not work all the time.
• Typically for silicon diodes, an applied voltage of 0.6V or greater is needed,
otherwise, the diode will not conduct.
• This feature is useful in forming a voltage-sensitive switch.
• I-V characteristics for silicon and germanium diodes is shown below.
12. Diode: How it doesn’t work
• When a diode is
connected to a battery as
shown, holes in the n-
side are forced to the
left while electrons in
the p-side are forced to
the right. This results in
an empty zone around
the pn- junction that is
free of charge carries
creating a depletion
region. This depletion
region acts as an
insulator preventing
current from flowing
through the diode.
When a diode is
arranged in this way, it
is said to be reverse-
biased. Reverse-biased (“closed door”)
Attracts holes Attracts electrons
13. Diode Applications —Half Wave Rectifier
•Diode converts ac input voltage to a pulsed dc output voltage.
•Whenever the ac input becomes negative at diode’s anode, the diode blocks current
flow.
– o/p voltage become zero.
•Diode introduces a 0.6V drop so o/p peak is 0.6V smaller than the i/p peak.
•The o/p frequency is same as the i/p frequency.
Vin
14. Diode Applications —Full Wave Rectifier
• A full-wave rectifier does not block negative swings in the i/p voltage, rather it
transforms them into positive swings at the o/p.
• To gain an understanding of device operation, follow current flow through pairs of
diodes in the bridge circuit.
• It is easily seen that one pair (D3-Rout-D2) allows current flow during the +ve half
cycle of Vin while the other pair (D4-Rout-D1) allows current flow during the -ve half
cycle of Vin.
– o/p voltage peak is 1.2V below the i/p voltage peak.
– The o/p frequency is twice the i/p frequency.
D1 D3
D2 D4
15. Diode Applications —AC2DC Power Supply
•An AC2DC power supply
is built using a transformer
and a full-wave rectifier.
•Transformer is used to
step down the voltage i/p.
•Rectifier converts AC to
pulsed DC.
•A filter capacitor is used
to smooth out the pulses.
•Capacitor must be large
enough to store sufficient
charge so as to provide a
steady current supply to the
load:
f is rectified signal’s
frequency (120Hz).
1/LoadR C f
16. Transistor
• A three lead semiconductor device that acts as:
– an electrically controlled switch, or
– a current amplifier.
• Transistor is analogous to a faucet.
– Turning faucet’s control knob alters the flow rate of water coming out from the faucet.
– A small voltage/current applied at transistor’s control lead controls a larger current flow
through its other two leads.
Water in
Water out
17. Transistor Types: BJT, JFET, and MOSFET
• Bipolar Junction Transistor (BJT)
– NPN and PNP
• Junction Field Effect Transistor (JFET)
– N-channel and P-channel
• Metal Oxide Semiconductor FET (MOSFET)
– Depletion type (n- and p-channel) and enhancement type (n- and p-channel)
BJT MOSFETJFET
18. BJT Types
• NPN and PNP.
– NPN: a small input current and a positive voltage applied @ its base (with VB>VE)
allows a large current to flow from collector to emitter.
– PNP: a small output current and a negative voltage @ its base (with VB<VE) allows a
much larger current to flow from emitter to collector.
19. NPN BJT: How it works — I
• When no voltage is applied at
transistor’s base, electrons in the
emitter are prevented from passing
to the collector side because of the
pn junction.
• If a negative voltage is applied to
the base, things get even worse as
the pn junction between the base
and emitter becomes reverse-
biased resulting in the formation of
a depletion region that prevents
current flow.
20. NPN BJT: How it works — II
• If a positive voltage (>0.6V) is
applied to the base of an npn
transistor, the pn junction between
the base and emitter becomes
forward-biased. During forward
bias, escaping electrons are drawn
to the positive base.
• Some electrons exit through the
base, but because the p-type base
is so thin, the onslaught of
electrons that leave the emitter get
close enough to the collector side
that they begin jumping into the
collector. Increasing the base
voltage increases the emitter-to-
collector electron flow.
• Recall, positive current flow is in
the direction opposite to the
electron flow current flows from
collector to emitter.
22. NPN Transistor in a Complete Circuit —I
NPN: VB = VEOFF
•Normally OFF.
•No current passes from collector to emitter when base is not activated.
23. NPN Transistor in a Complete Circuit —II
NPN: VB > VE ON
• When VB > VE we have an operating circuit.
• Current passes from collector to emitter when base is activated.
25. JFET
• Junction field effect transistors like BJTs are three lead
semiconductor devices.
• JFETs are used as:
– electrically controlled switches,
– current amplifiers, and
– voltage-controlled resistors.
• Unlike BJTs, JFETs do not require a bias current and are controlled
by using only a voltage.
• JFETs are normally on when VG - VS = 0.
• When VG - VS 0, then JFETs become resistive to current flow
through the drain-source pair “JFETs are depletion devices.”
26. JFET Types
• Two types of JFETs:
– n-channel and p-channel.
• In n-channel JFET, a –ve voltage applied @ its gate (with VG < VS) reduces current
flow from drain to source. It operates with VD > VS.
• In p-channel JFET, a +ve voltage applied @ its gate (with VG > VS) reduces current
flow from source to drain. It operates with VS > VD.
• JFETs have very high input impedance and draw little or no input current
– if there is any circuit/component connected to the gate of a JFET, no current is drawn
away from or sunk into this circuit.
27. MOSFET
• Metal oxide semiconductor FET.
• Similar to JFET.
• A metal oxide insulator is placed @ the gate to obtain a high input impedance @ the
gate
– gate input impedance approx. 1014Ω.
• Use of insulator as described above yields a low gate-to-channel capacitance.
– If too much static electricity builds up on the gate, then the MOSFET may be damaged.
28. MOSFET Types
• Enhancement type:
– Normally off, thus no current flows through drain-source channel when VG = VS.
– When a voltage applied @ the gate causes VG VS the drain-source channel reduces
resistance to current flow.
• Depletion type:
– Normally on, thus maximum current flows through drain-source channel when VG = VS.
– When a voltage applied @ the gate causes VG VS the drain-source channel increases
resistance to current flow.
VG < VS VG > VSVG > VS VG < VS
Current flow increases with: Current flow decreases with:
29. Optoelectronics
Light emitting diodes Infrared detector
• In optoelectronics we deal with 2 types of electronic devices.
• Light emitting electronic devices: ones that generate electromagnetic energy under
the action of electrical field. Example: light emitting diodes (visible and infrared
light).
• Light detecting devices: ones that transform electromagnetic energy input into
electrical current/voltage. Examples: photoresistors, photodiodes, phototransistors,
etc.
31. LED 101— I
• 2 lead semiconductor device.
• Light emitting PN-junction diode.
– Visible or infrared light.
• Has polarity.
• Recall diodes act as a one way gate to current flow.
– A forward-biased PN-junction diode allows current flow from anode to cathode.
• An LED conducts and emits light when its anode is made more positive (approx.
1.4V) than its cathode.
– With reverse polarity, LED stops conducting and emitting light.
32. LED 101— II
• Similar to diodes, LEDs are current-dependent devices.
– LED brightness is controlled by controlling current through LED.
• Too little current through LED LED remains OFF.
• Small current through LED dimly lit LED.
• Large current through LED brightly lit LED.
• Too much current through LED LED is destroyed.
• A resistor placed in series with LED accomplishes current control
+
Anode
-
Cathode
LED symbol
33. LED 101—III
• Let Vs be the supply voltage.
• Let Vf be the required forward bias voltage for the
LED.
• Let I be the desired current flow through LED.
• Then, the current limiting resistance R is sized as
follow:
• If R is chosen smaller than the above value, a
larger current will flow through the LED.
– LEDs can handle only limited current (varies from
20mA to 100mA).
– If current through LED is larger than the maximum
allowed value, than the LED will be damaged.
Vs
Vf
VRI
R
R s f
s fR
V V V
V VV
R
I I
34. Visible-Light LED
• Inexpensive and durable.
• Typical usage: as indicator lights.
• Common colors: green (~565nm), yellow (~585nm), orange (~615nm), and red
(~650nm).
• Maximum forward voltage: 1.8V.
• Typical operating currents: 1 to 3mA.
• Typical brightness levels: 1.0 to 3.0mcd/1mA to 3.0mcd /2mA.
• High-brightness LEDs exist.
– Used in high-brightness flashers (e.g., bicycle flashers).
35. Blinking LED
• Contain a miniature integrated circuit that causes LED to flash from 1 to 6 times/second.
• Typical usage: indicator flashers. May also be used as simple oscillators.
36. Tricolor LED
• Two LEDs placed in parallel facing opposite directions.
• One LED is red or orange, the other is green.
• Current flow in one direction turns one LED ON while the other remains OFF due
to reverse bias.
• Current flow in the other direction turns the first LED OFF and the second LED ON.
• Rapid switching of current flow direction will alternatively turn the two LEDs ON
giving yellow light.
• Used as a polarity indicator.
• Maximum voltage rating: 3V
• Operating range: 10 to 20mA
37. 7-Segment LED Display
• Used for displaying numbers and other characters.
• 7 individual LEDs are used to make up the display.
• When a voltage is applied across one of the LEDs, a portion of the 8 lights up.
• Unlike liquid crystal displays (LCD), 7-segment LED displays tend to be more
rugged, but they also consume more power.
38. How LED Works
• The light-emitting section of an LED is made by joining n-type and p-type semiconductors
together to form a pn junction.
• When the pn junction is forward-biased, electrons in the n side are excited across the pn
junction and into the p side, where they combine with holes.
• As the electrons combine with the holes, photons are emitted.
• The pn-junction section of an LED is encased in an epoxy shell that is doped with light
scattering particles to diffuse light and make the LED appear brighter.
• Often a reflector placed beneath the semiconductor is used to direct the light upward.
39. Photoresistors —I
• Light sensitive variable resistors.
• Its resistance depends on the intensity of light incident upon it.
– Under dark condition, resistance is quite high (M: called dark resistance).
– Under bright condition, resistance is lowered (few hundred ).
• Response time:
– When a photoresistor is exposed to light, it takes a few milliseconds, before it
lowers its resistance.
– When a photoresistor experiences removal of light, it may take a few seconds
to return to its dark resistance.
Symbol
40. Photoresistors —II
• Some photoresistors respond better to light that contains
photons within a particular wavelength of spectrum.
– Example: Cadmium-sulfide photoresistos respond to
light within 400-800nm range.
– Example: Lead-sulfide photoresistos respond to infrared
light.
41. How Photoresistor Works
• Special semiconductor crystal, such as cadmium sulfide or lead sulfide is used to make
photoresistors.
• When this semiconductor is placed in dark, electrons within its structure resist flow through
the resistor because they are too strongly bound to the crystal’s atoms.
• When this semiconductor is illuminated, incoming photons of light collide with the bound
electrons, stripping them from the binding atom, thus creating holes in the process.
• Liberated electrons contribute to the current flowing through the device.
42. Photoresistor Application —Light Activated Relay
• Light-sensitive voltage divider is being
used to trip a relay whenever the light
intensity change.
• Light-activated circuit:
– When the photoresistor is exposed to
light, its resistance decreases.
– Transistor’s base current and
voltage increase and if the base current
and voltage are large enough, the
collector-emitter pair of the transistor
conducts triggering the relay.
• The value of R1 in the light-activated
circuit should be around 1 KΩ but
may have to be adjusted.
• Dark-activated relay works in a similar
but opposite manner.
• R1 in the dark-activated circuit
(100KΩ) may also have to be adjusted.
• A 6 to 9-V relay with a 500Ω coil can
be used in either circuit.
Light activated relay Dark activated relay
43. Photodiode
• Photodiode is a 2 lead semiconductor device that transforms light energy to electric
current.
• Suppose anode and cathode of a photodiode are wired to a current meter.
– When photodiode is placed in dark, the current meter displays zero current flow.
– When the photodiode is expose to light, it acts a a current source, causing current flow
from cathode to anode of photodiode through the current meter.
• Photodiodes have very linear light v/s current characteristics.
– Commonly used as light meters in cameras.
• Photodiodes often have built-in lenses and optical filters.
• Response time of a photodiode slows with increasing surface area.
• Photodiodes are more sensitive than photoresistor.
Symbol
44. How Photodiode Works
• Photodiode: A thin n-type
semiconductor sandwiched with a
thicker p-type semiconductor.
• N-side is cathode, p-side is anode.
• Upon illumination, a # of photons pass
from the n-side and into the p-side of
photodiode.
– Some photons making it into p-side
collide with bound electrons within p-
semiconductor, ejecting them and
creating holes.
– If these collisions are close to the pn-
interface, the ejected electrons cross the
junction, yielding extra electrons on the
n-side and extra holes on the p-side.
– Segregation of +ve and -ve charges
leads to a potential difference across the
pn-junction.
– When a wire is connected between the
cathode and anode, a conventionally
positive current flow from the anode to
cathode
45. Photodiode Applications—Photovoltaic Current Source
• Photodiode converts light energy directly into electric current that can be
measured with meter.
• The input intensity of light and the output current are nearly linear.
46. • Solar cells are photodiodes with very large surface areas.
• Compared to usual photodiodes, the large surface area in photodiode of a
solar cell yields
– a device that is more sensitive to incoming light.
– a device that yields more power (larger current/volts).
• Solar cells yield more power.
• A single solar cell may provide up to 0.5V that can supply 0.1A when
exposed to bright light.
Solar Cell—I
48. Solar Cell Basic Operation—Power Sources
• Each solar cell produces an
open-circuit voltage from
around 0.45 to 0.5 V and may
generate as much as 0.1 A in
bright light.
• Similar to batteries, solar cells
can be combined in series or
parallel.
• Adding cells in series, yields
output voltage that is the sum
of the individual cell voltages.
• Adding solar cells in parallel,
yields an increased output
current vis-à-vis a single solar
cell.
49. Solar Cell Basic Operation—Battery Charger
• Nine solar cells placed in series can
be used to recharge two 1.5 V NiCd
cells.
• The diode is added to the circuit to
prevent the NiCd cells from
discharging through the solar cell
during times of darkness.
• It is important not to exceed the safe
charging rate of NiCd cells. To slow
the charge rate, a resistor can be
placed in series with the batteries.
50. Phototransistor
• Phototransistor is a light sensitive transistor.
• In one common type of phototransistor, the base lead of a BJT is replaced by a light
sensitive surface.
• When the light sensitive surface @ the base is kept in darkness, the collector-emitter
pair of the BJT does not conduct.
• When the light sensitive surface @ the base is exposed to light, a small amount of
current flows from the base to the emitter. The small base-emitter current controls
the larger collector-emitter current.
• Alternatively, one can also use a field-effect phototransistor (Photo FET).
• In a photo FET, the light exposure generates a gate voltage which controls a
drain-source current.
Phototransistor Photo FET
51. How Phototransistor Works
• The bipolar phototransistor resembles a
bipolar transistor that has extra large p-type
semiconductor region that is open for light
exposure.
• When photons from a light source collide
with electrons within the p-type
semiconductor, they gain enough energy to
jump across the pn-junction energy barrier-
provided the photons are of the right
frequency/energy.
• As electrons jump from the p-region into the
lower n-region, holes are created in the p-
type semiconductor.
• The extra electrons injected into the lower n-
type slab are drawn toward the positive
terminal of the battery, while electrons from
the negative terminal of the battery are draw
into the upper n-type semiconductor and
across the np junction, where they combine
with the holes, the net result is an electrons
current that flows from the emitter to the
collector.
52. Phototransistor Applications—Light Activated Relay
• A phototransistor is used to control the base current supplied to a power-switching
transistor that is used to supply current to a relay.
• When light comes in contact with the phototransistor, the phototransistor turns on,
allowing current to pass from the supply into the base of the power-switching
transistor.
• This allows the power-switching transistor to turns on, and current flows through the
relay, triggering it to switch states.
• The 100K pot is used to adjust the sensitivity of device by controlling current flow
through the phototransistor.
53. Phototransistor Applications—Dark Activated Relay
• A phototransistor is used to control the base current supplied to a power-switching
transistor that is used to supply current to a relay.
• When light is removed from the phototransistor, the phototransistor turns off,
allowing more current to enter into the base of the power-switching transistor.
• This allows the power-switching transistor to turns on, and current flows through
the relay, triggering it to switch states.
• The 100K pot is used to adjust the sensitivity of device by controlling current flow
through the phototransistor.
54. Phototransistor Applications—Tachometer
• A phototransistor is being used as a frequency counter or tachometer.
• A rotating disk is connected to a rotating shaft. The rotating disk has one hole in it.
• For the given setup, the disk will allow light to pass through the hole once every
revolution.
• The light passing through the disk triggers the phototransistor into conduction.
• A frequency counter is used to count the number of electrical pulses generated.