This document provides information on basic electronics components:
- Semiconductors like silicon can have their conductivity controlled, making them useful for electronic devices. Silicon is the most common semiconductor material.
- "Doping" silicon with atoms like phosphorus or boron creates N-type or P-type silicon respectively. Combining N-type and P-type silicon creates a diode, which allows current to flow in only one direction.
- Other components like transistors can act as electrically controlled switches, amplifying small input signals into larger output signals. Bipolar junction transistors (BJT), junction field effect transistors (JFET), and metal-oxide-semiconductor field effect transistors (MOSFET)
This document provides an introduction to the physics of photovoltaic devices. It discusses key concepts such as the pn junction, band diagrams, carrier transport mechanisms, and the operation of solar cells under illumination and bias. The document also describes factors that influence solar cell performance such as thickness, resistances, temperature, and illumination intensity.
When a voltage is applied to a diode, electrons flow from the N-type side through the depletion zone and into the P-type side if the diode is forward biased. This causes current to flow. If the voltage is reversed, the depletion zone widens and no current flows, making the diode act as an open switch. Diodes can be used as rectifiers to convert AC to DC or as switches that allow current in one direction but not the other depending on bias polarity.
The document discusses recent trends in photonic devices. It begins by defining optics and photonics, and describes some applications of photonics including information technology, healthcare, sensing, lighting and displays. It then explains that photonic devices manipulate or detect light, providing examples like lasers, LEDs and solar cells. The document goes on to discuss latest trends like nanophotonics using graphene, carbon nanotubes and photonic crystals. It also covers silicon photonic devices using silicon-germanium transistors and germanium-tin phototransistors. In conclusion, it predicts future applications of photonics in areas like e-paper, solar panels and light-emitting fabrics.
Solar photovoltaic cells convert light energy from photons into electrical energy through the photovoltaic effect. When photons hit the solar cell, they excite electrons which are then pulled away before they can relax, generating a current. The efficiency and performance of solar cells depends on factors like material bandgap, cell temperature, and resistance. Different cell types like single crystal, polycrystalline, and amorphous thin films are fabricated through various processes to optimize these factors and harness solar energy on a large scale.
This document discusses integrated circuit technology. It begins with an overview of the IC market breakdown by sector. It then discusses advantages of ICs such as smaller size, higher speed, lower power consumption compared to discrete components. The document provides a history of important IC inventions from 1904 to the present. It also discusses transistor scaling that has allowed achieving more complex ICs through reduced dimensions over time. Finally, it covers different IC design styles such as full custom, standard cell, gate array, and FPGA and their tradeoffs in terms of performance, cost, area, and time-to-market.
The attached narrated power point presentation explains the construction, working and applications of PN Junction Diodes. The material will be useful for KTU first year students who prepare for the subject EST 130, Part B, Basic Electronics Engineering.
A p-n junction is formed where a single crystal of silicon or germanium is doped such that one half is p-type semiconductor and the other half is n-type semiconductor. When forward biased, the barrier potential decreases allowing majority charge carriers to flow across the junction, decreasing resistance. When reverse biased, the barrier potential increases preventing carrier flow and increasing resistance. The voltage-current characteristics of a p-n junction diode are nonlinear, with negligible current below the threshold voltage and exponential increase in current above it. In reverse bias, very little reverse saturation current flows until the breakdown voltage is exceeded.
This document discusses ultrasonic waves and methods for their production. It provides details on two main production methods: magneto-striction and piezo-electric. Magneto-striction uses a ferromagnetic rod subjected to an alternating magnetic field to produce vibrations. Piezo-electric uses crystals like quartz that produce electricity when pressure is applied, allowing for vibrations. The document also briefly explains how sonar uses ultrasonic waves to detect underwater objects by timing beam emission and reflection.
This document provides an introduction to the physics of photovoltaic devices. It discusses key concepts such as the pn junction, band diagrams, carrier transport mechanisms, and the operation of solar cells under illumination and bias. The document also describes factors that influence solar cell performance such as thickness, resistances, temperature, and illumination intensity.
When a voltage is applied to a diode, electrons flow from the N-type side through the depletion zone and into the P-type side if the diode is forward biased. This causes current to flow. If the voltage is reversed, the depletion zone widens and no current flows, making the diode act as an open switch. Diodes can be used as rectifiers to convert AC to DC or as switches that allow current in one direction but not the other depending on bias polarity.
The document discusses recent trends in photonic devices. It begins by defining optics and photonics, and describes some applications of photonics including information technology, healthcare, sensing, lighting and displays. It then explains that photonic devices manipulate or detect light, providing examples like lasers, LEDs and solar cells. The document goes on to discuss latest trends like nanophotonics using graphene, carbon nanotubes and photonic crystals. It also covers silicon photonic devices using silicon-germanium transistors and germanium-tin phototransistors. In conclusion, it predicts future applications of photonics in areas like e-paper, solar panels and light-emitting fabrics.
Solar photovoltaic cells convert light energy from photons into electrical energy through the photovoltaic effect. When photons hit the solar cell, they excite electrons which are then pulled away before they can relax, generating a current. The efficiency and performance of solar cells depends on factors like material bandgap, cell temperature, and resistance. Different cell types like single crystal, polycrystalline, and amorphous thin films are fabricated through various processes to optimize these factors and harness solar energy on a large scale.
This document discusses integrated circuit technology. It begins with an overview of the IC market breakdown by sector. It then discusses advantages of ICs such as smaller size, higher speed, lower power consumption compared to discrete components. The document provides a history of important IC inventions from 1904 to the present. It also discusses transistor scaling that has allowed achieving more complex ICs through reduced dimensions over time. Finally, it covers different IC design styles such as full custom, standard cell, gate array, and FPGA and their tradeoffs in terms of performance, cost, area, and time-to-market.
The attached narrated power point presentation explains the construction, working and applications of PN Junction Diodes. The material will be useful for KTU first year students who prepare for the subject EST 130, Part B, Basic Electronics Engineering.
A p-n junction is formed where a single crystal of silicon or germanium is doped such that one half is p-type semiconductor and the other half is n-type semiconductor. When forward biased, the barrier potential decreases allowing majority charge carriers to flow across the junction, decreasing resistance. When reverse biased, the barrier potential increases preventing carrier flow and increasing resistance. The voltage-current characteristics of a p-n junction diode are nonlinear, with negligible current below the threshold voltage and exponential increase in current above it. In reverse bias, very little reverse saturation current flows until the breakdown voltage is exceeded.
This document discusses ultrasonic waves and methods for their production. It provides details on two main production methods: magneto-striction and piezo-electric. Magneto-striction uses a ferromagnetic rod subjected to an alternating magnetic field to produce vibrations. Piezo-electric uses crystals like quartz that produce electricity when pressure is applied, allowing for vibrations. The document also briefly explains how sonar uses ultrasonic waves to detect underwater objects by timing beam emission and reflection.
There are four main methods of transistor biasing: base resistor method, emitter bias method, biasing with collector feedback resistor, and voltage-divider bias method. The document then focuses on explaining the base resistor method and voltage-divider bias method in more detail. For the base resistor method, a resistor is used to provide base current, but it has poor stability. For the voltage-divider bias method, two resistors are used to provide stable biasing of the transistor by controlling the base-emitter voltage. This method is widely used due to its stability from the emitter resistor preventing changes in collector current.
A Zener diode is a type of diode that permits current not only in the forward direction like a normal diode, but also in the reverse direction if the voltage is larger than the breakdown voltage known as “Zener knee voltage” or “Zener voltage”.
The device is named after American physicist Clarence Melvin Zener, who first described the ZENER EFFECT in1934. Later his work led to the BELL LABS implantation of the effect in form of an electronic device, the ZENER DIODE.
Zener diodes are a modified form of PN silicon diode used extensively for voltage regulation. The P type and N type silicon used is doped more heavily than a standard PN diode.
This causes a very thin depletion region. The zener diodes breakdown characteristics are determined by the doping process
Zeners are commercially available with voltage breakdowns of 1.8 V to 200 V.
When a Zener diode is forward biased, it operates as a normal diode.
In forward biased P side connected to positive and N side connected to negative terminal of battery. In this case the electrons and holes are swept across the junction and large current flow through it.
In case of reverse biased current practically zero and at certain voltage which called Zener voltage the current increases sharply.
Each Zener diode has breakdown rating which specifies the max voltage that can be dropped across it.
Zener diodes are designed to operate in reverse breakdown. Two types of reverse breakdown in a zener diode are AVALANCHE and ZENER. The avalanche break down occurs in both rectifier and zener diodes at a sufficiently high reverse voltage. Zener breakdown occurs in a zener diode at low reverse voltages.
A Zener allows current to flow in the reverse direction when the voltage is above a certain value known as the breakdown voltage, "Zener knee voltage", "Zener voltage", “Avalanche point", or “Peak inverse voltage”
Breakdown Characteristics : Figure 2 shows the reverse portion of a zener diode’s characteristic curve. As the reverse voltage (푉_푅 ) is increased, the reverse current (퐼_푅 ) remains extremely small up to the “knee” of the curve. The reverse current is also called the zener current, 퐼_푍 . At this point, the breakdown effect begins; the internal zener resistance, also called zener impedance (푍_푍), begins to decrease as reverse current increases rapidly.Voltage Regulator :In a DC circuit, Zener diode can be used as a voltage regulator to regulate the voltage across small circuits.
Waveform Clipper :Zener diode can be used to make a Waveform Clipper. Two Zener diodes facing each other in series will act to clip both halves of an input signal.
Voltage Shifter :A Zener diode can be applied to a circuit with a resistor to act as a voltage shifter. This circuit lowers the output voltage by a quantity that is equal to the Zener diode's breakdown voltage.
Tunnel diodes are heavily doped PN junction diodes that exhibit negative resistance. They were invented in 1958 by Dr. Leo Esaki and operate based on the quantum mechanical principle of tunneling. When forward biased, the current initially increases with voltage but then decreases as the voltage is further increased, demonstrating the unique property of negative resistance. Tunnel diodes find application in ultrafast switching, memory storage, satellite communication equipment, and oscillators due to their negative resistance characteristic.
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.
The document discusses the physics of semiconductors including PN junction diodes and resistors. It covers semiconductor fundamentals like doping and intrinsic nature. It describes how doping materials like phosphorus or boron create N-type or P-type semiconductors. When an N-type and P-type material come into contact, a PN junction is formed with a depletion region and electric field. A PN junction acts as a switch that only allows current in one direction depending on whether it is forward or reverse biased.
This document discusses full wave rectifier circuits. It defines a full wave rectifier as a circuit that converts AC voltage to pulsating DC voltage using both half cycles of the input voltage. It then describes two types of full wave rectifiers: 1) a center tapped full wave rectifier that uses two diodes connected to the center tapped secondary winding of a transformer, and 2) a full wave bridge rectifier that uses four diodes arranged in a bridge configuration without needing a center tapped transformer. The document concludes by stating that a full wave rectifier allows for almost all incoming AC power to be converted to DC.
Bu sunum; Gazi Üniversitesi İleri Teknolojiler ABD, Doc.Dr Sema BİLGE OCAK 'ın sorumluluğunda olan" Radyasyon Algılama Sistemleri" adlı derste sunmuş olduğum Radyasyonun Madde ile etkileşimini detaylı bir şekilde anlatmaktadır.
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.
A diode is an electronic component with two electrodes called the anode and cathode. It allows current to flow easily in one direction but blocks it in the other. The document discusses the theory of operation of a PN junction diode, including how applying different biases (zero, forward, reverse) changes the width of the depletion region and thus the diode's conductivity. Key aspects covered are the diode's I-V characteristics curve, forward and reverse bias regions, and breakdown voltage. Useful parameters like maximum forward current and forward voltage drop are also defined.
This document provides notes on electronic devices and circuits from Lendi Institute of Engineering and Technology. It begins with definitions of key terms like electronic device, circuit, and semiconductor. It then discusses semiconductor materials like silicon, germanium, and gallium arsenide. It compares the properties of insulators, semiconductors, and conductors based on factors like conductivity, resistivity, and band structure. Examples of materials in each category are given along with diagrams. The document continues with explanations of energy levels and band structures in insulators, semiconductors, and metals. In summary, the document provides introductory concepts on electronic devices, circuits, and semiconductor physics.
This document discusses the formation and operation of p-n junction diodes. It describes three common methods for forming a p-n junction: alloying, diffusion, and vapor deposition. It explains key concepts such as the depletion region, barrier potential, drift and diffusion currents, and forward and reverse biasing. Forward biasing decreases the width of the depletion region, allowing majority carriers to flow more easily across the junction and conduct current.
The document studies the performance of FINFET transistors with respect to width and height. FINFET is a non-planar, double or tri-gate transistor built on a silicon-on-insulator substrate. It has lower leakage currents, reduced short-channel effects, and allows for more transistors per unit area due to its 3D structure. The study found that reducing the width of the FIN can decrease the threshold voltage, while keeping the height similar.
This document discusses bipolar junction transistors (BJTs) and field effect transistors (FETs). It provides information on:
1. The material structure and operation regions of BJTs, including active, cutoff, and saturation regions where the transistor acts as an amplifier, open switch, and closed switch respectively.
2. Maximum ratings for the P2N2222A BJT transistor.
3. The material structure of FETs which use a gate voltage to control current flow, making them voltage-operated devices.
4. The operation regions of FETs including cutoff, ohmic/linear, and saturation regions and descriptions of each.
5. Maximum ratings for the J111
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 the electric field due to an electric dipole at points on and off its axial line. It describes how the electric field is calculated on the axial line and equatorial plane. For large distances, the electric field decreases faster for a dipole than a point charge, and the direction of the field also changes on and off the axial line. A point dipole is defined as one where the charge separation approaches zero but the dipole moment remains finite. The document also discusses the torque experienced by a dipole placed in a uniform electric field and how microwaves work by producing torque on the electric dipole of water molecules to heat food.
The document discusses the history and development of solar power as an alternative renewable energy source. It describes how concerns over dependency on non-renewable energy in the 1970s led scientists to research new sources. Their work established solar power generated through concentrating solar and photovoltaic methods. The document then provides details on the technology behind solar cells and panels, and how they are able to convert sunlight into usable electricity through photovoltaic effects and semiconductor materials.
Mosfet
MOSFETs have characteristics similar to JFETs and additional characteristics that make them very useful.
There are 2 types:
• Depletion-Type MOSFET
• Enhancement-Type MOSFET
The MOSFET is an important element in embedded system design which is used to control the loads as per the requirement. The MOSFET is a high voltage controlling device provides some key features for circuit designers in terms of their overall performance.
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.
There are four main methods of transistor biasing: base resistor method, emitter bias method, biasing with collector feedback resistor, and voltage-divider bias method. The document then focuses on explaining the base resistor method and voltage-divider bias method in more detail. For the base resistor method, a resistor is used to provide base current, but it has poor stability. For the voltage-divider bias method, two resistors are used to provide stable biasing of the transistor by controlling the base-emitter voltage. This method is widely used due to its stability from the emitter resistor preventing changes in collector current.
A Zener diode is a type of diode that permits current not only in the forward direction like a normal diode, but also in the reverse direction if the voltage is larger than the breakdown voltage known as “Zener knee voltage” or “Zener voltage”.
The device is named after American physicist Clarence Melvin Zener, who first described the ZENER EFFECT in1934. Later his work led to the BELL LABS implantation of the effect in form of an electronic device, the ZENER DIODE.
Zener diodes are a modified form of PN silicon diode used extensively for voltage regulation. The P type and N type silicon used is doped more heavily than a standard PN diode.
This causes a very thin depletion region. The zener diodes breakdown characteristics are determined by the doping process
Zeners are commercially available with voltage breakdowns of 1.8 V to 200 V.
When a Zener diode is forward biased, it operates as a normal diode.
In forward biased P side connected to positive and N side connected to negative terminal of battery. In this case the electrons and holes are swept across the junction and large current flow through it.
In case of reverse biased current practically zero and at certain voltage which called Zener voltage the current increases sharply.
Each Zener diode has breakdown rating which specifies the max voltage that can be dropped across it.
Zener diodes are designed to operate in reverse breakdown. Two types of reverse breakdown in a zener diode are AVALANCHE and ZENER. The avalanche break down occurs in both rectifier and zener diodes at a sufficiently high reverse voltage. Zener breakdown occurs in a zener diode at low reverse voltages.
A Zener allows current to flow in the reverse direction when the voltage is above a certain value known as the breakdown voltage, "Zener knee voltage", "Zener voltage", “Avalanche point", or “Peak inverse voltage”
Breakdown Characteristics : Figure 2 shows the reverse portion of a zener diode’s characteristic curve. As the reverse voltage (푉_푅 ) is increased, the reverse current (퐼_푅 ) remains extremely small up to the “knee” of the curve. The reverse current is also called the zener current, 퐼_푍 . At this point, the breakdown effect begins; the internal zener resistance, also called zener impedance (푍_푍), begins to decrease as reverse current increases rapidly.Voltage Regulator :In a DC circuit, Zener diode can be used as a voltage regulator to regulate the voltage across small circuits.
Waveform Clipper :Zener diode can be used to make a Waveform Clipper. Two Zener diodes facing each other in series will act to clip both halves of an input signal.
Voltage Shifter :A Zener diode can be applied to a circuit with a resistor to act as a voltage shifter. This circuit lowers the output voltage by a quantity that is equal to the Zener diode's breakdown voltage.
Tunnel diodes are heavily doped PN junction diodes that exhibit negative resistance. They were invented in 1958 by Dr. Leo Esaki and operate based on the quantum mechanical principle of tunneling. When forward biased, the current initially increases with voltage but then decreases as the voltage is further increased, demonstrating the unique property of negative resistance. Tunnel diodes find application in ultrafast switching, memory storage, satellite communication equipment, and oscillators due to their negative resistance characteristic.
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.
The document discusses the physics of semiconductors including PN junction diodes and resistors. It covers semiconductor fundamentals like doping and intrinsic nature. It describes how doping materials like phosphorus or boron create N-type or P-type semiconductors. When an N-type and P-type material come into contact, a PN junction is formed with a depletion region and electric field. A PN junction acts as a switch that only allows current in one direction depending on whether it is forward or reverse biased.
This document discusses full wave rectifier circuits. It defines a full wave rectifier as a circuit that converts AC voltage to pulsating DC voltage using both half cycles of the input voltage. It then describes two types of full wave rectifiers: 1) a center tapped full wave rectifier that uses two diodes connected to the center tapped secondary winding of a transformer, and 2) a full wave bridge rectifier that uses four diodes arranged in a bridge configuration without needing a center tapped transformer. The document concludes by stating that a full wave rectifier allows for almost all incoming AC power to be converted to DC.
Bu sunum; Gazi Üniversitesi İleri Teknolojiler ABD, Doc.Dr Sema BİLGE OCAK 'ın sorumluluğunda olan" Radyasyon Algılama Sistemleri" adlı derste sunmuş olduğum Radyasyonun Madde ile etkileşimini detaylı bir şekilde anlatmaktadır.
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.
A diode is an electronic component with two electrodes called the anode and cathode. It allows current to flow easily in one direction but blocks it in the other. The document discusses the theory of operation of a PN junction diode, including how applying different biases (zero, forward, reverse) changes the width of the depletion region and thus the diode's conductivity. Key aspects covered are the diode's I-V characteristics curve, forward and reverse bias regions, and breakdown voltage. Useful parameters like maximum forward current and forward voltage drop are also defined.
This document provides notes on electronic devices and circuits from Lendi Institute of Engineering and Technology. It begins with definitions of key terms like electronic device, circuit, and semiconductor. It then discusses semiconductor materials like silicon, germanium, and gallium arsenide. It compares the properties of insulators, semiconductors, and conductors based on factors like conductivity, resistivity, and band structure. Examples of materials in each category are given along with diagrams. The document continues with explanations of energy levels and band structures in insulators, semiconductors, and metals. In summary, the document provides introductory concepts on electronic devices, circuits, and semiconductor physics.
This document discusses the formation and operation of p-n junction diodes. It describes three common methods for forming a p-n junction: alloying, diffusion, and vapor deposition. It explains key concepts such as the depletion region, barrier potential, drift and diffusion currents, and forward and reverse biasing. Forward biasing decreases the width of the depletion region, allowing majority carriers to flow more easily across the junction and conduct current.
The document studies the performance of FINFET transistors with respect to width and height. FINFET is a non-planar, double or tri-gate transistor built on a silicon-on-insulator substrate. It has lower leakage currents, reduced short-channel effects, and allows for more transistors per unit area due to its 3D structure. The study found that reducing the width of the FIN can decrease the threshold voltage, while keeping the height similar.
This document discusses bipolar junction transistors (BJTs) and field effect transistors (FETs). It provides information on:
1. The material structure and operation regions of BJTs, including active, cutoff, and saturation regions where the transistor acts as an amplifier, open switch, and closed switch respectively.
2. Maximum ratings for the P2N2222A BJT transistor.
3. The material structure of FETs which use a gate voltage to control current flow, making them voltage-operated devices.
4. The operation regions of FETs including cutoff, ohmic/linear, and saturation regions and descriptions of each.
5. Maximum ratings for the J111
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 the electric field due to an electric dipole at points on and off its axial line. It describes how the electric field is calculated on the axial line and equatorial plane. For large distances, the electric field decreases faster for a dipole than a point charge, and the direction of the field also changes on and off the axial line. A point dipole is defined as one where the charge separation approaches zero but the dipole moment remains finite. The document also discusses the torque experienced by a dipole placed in a uniform electric field and how microwaves work by producing torque on the electric dipole of water molecules to heat food.
The document discusses the history and development of solar power as an alternative renewable energy source. It describes how concerns over dependency on non-renewable energy in the 1970s led scientists to research new sources. Their work established solar power generated through concentrating solar and photovoltaic methods. The document then provides details on the technology behind solar cells and panels, and how they are able to convert sunlight into usable electricity through photovoltaic effects and semiconductor materials.
Mosfet
MOSFETs have characteristics similar to JFETs and additional characteristics that make them very useful.
There are 2 types:
• Depletion-Type MOSFET
• Enhancement-Type MOSFET
The MOSFET is an important element in embedded system design which is used to control the loads as per the requirement. The MOSFET is a high voltage controlling device provides some key features for circuit designers in terms of their overall performance.
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.
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.
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.
EWOCS-I: The catalog of X-ray sources in Westerlund 1 from the Extended Weste...Sérgio Sacani
Context. With a mass exceeding several 104 M⊙ and a rich and dense population of massive stars, supermassive young star clusters
represent the most massive star-forming environment that is dominated by the feedback from massive stars and gravitational interactions
among stars.
Aims. In this paper we present the Extended Westerlund 1 and 2 Open Clusters Survey (EWOCS) project, which aims to investigate
the influence of the starburst environment on the formation of stars and planets, and on the evolution of both low and high mass stars.
The primary targets of this project are Westerlund 1 and 2, the closest supermassive star clusters to the Sun.
Methods. The project is based primarily on recent observations conducted with the Chandra and JWST observatories. Specifically,
the Chandra survey of Westerlund 1 consists of 36 new ACIS-I observations, nearly co-pointed, for a total exposure time of 1 Msec.
Additionally, we included 8 archival Chandra/ACIS-S observations. This paper presents the resulting catalog of X-ray sources within
and around Westerlund 1. Sources were detected by combining various existing methods, and photon extraction and source validation
were carried out using the ACIS-Extract software.
Results. The EWOCS X-ray catalog comprises 5963 validated sources out of the 9420 initially provided to ACIS-Extract, reaching a
photon flux threshold of approximately 2 × 10−8 photons cm−2
s
−1
. The X-ray sources exhibit a highly concentrated spatial distribution,
with 1075 sources located within the central 1 arcmin. We have successfully detected X-ray emissions from 126 out of the 166 known
massive stars of the cluster, and we have collected over 71 000 photons from the magnetar CXO J164710.20-455217.
ESPP presentation to EU Waste Water Network, 4th June 2024 “EU policies driving nutrient removal and recycling
and the revised UWWTD (Urban Waste Water Treatment Directive)”
The use of Nauplii and metanauplii artemia in aquaculture (brine shrimp).pptxMAGOTI ERNEST
Although Artemia has been known to man for centuries, its use as a food for the culture of larval organisms apparently began only in the 1930s, when several investigators found that it made an excellent food for newly hatched fish larvae (Litvinenko et al., 2023). As aquaculture developed in the 1960s and ‘70s, the use of Artemia also became more widespread, due both to its convenience and to its nutritional value for larval organisms (Arenas-Pardo et al., 2024). The fact that Artemia dormant cysts can be stored for long periods in cans, and then used as an off-the-shelf food requiring only 24 h of incubation makes them the most convenient, least labor-intensive, live food available for aquaculture (Sorgeloos & Roubach, 2021). The nutritional value of Artemia, especially for marine organisms, is not constant, but varies both geographically and temporally. During the last decade, however, both the causes of Artemia nutritional variability and methods to improve poorquality Artemia have been identified (Loufi et al., 2024).
Brine shrimp (Artemia spp.) are used in marine aquaculture worldwide. Annually, more than 2,000 metric tons of dry cysts are used for cultivation of fish, crustacean, and shellfish larva. Brine shrimp are important to aquaculture because newly hatched brine shrimp nauplii (larvae) provide a food source for many fish fry (Mozanzadeh et al., 2021). Culture and harvesting of brine shrimp eggs represents another aspect of the aquaculture industry. Nauplii and metanauplii of Artemia, commonly known as brine shrimp, play a crucial role in aquaculture due to their nutritional value and suitability as live feed for many aquatic species, particularly in larval stages (Sorgeloos & Roubach, 2021).
Remote Sensing and Computational, Evolutionary, Supercomputing, and Intellige...University of Maribor
Slides from talk:
Aleš Zamuda: Remote Sensing and Computational, Evolutionary, Supercomputing, and Intelligent Systems.
11th International Conference on Electrical, Electronics and Computer Engineering (IcETRAN), Niš, 3-6 June 2024
Inter-Society Networking Panel GRSS/MTT-S/CIS Panel Session: Promoting Connection and Cooperation
https://www.etran.rs/2024/en/home-english/
Immersive Learning That Works: Research Grounding and Paths ForwardLeonel Morgado
We will metaverse into the essence of immersive learning, into its three dimensions and conceptual models. This approach encompasses elements from teaching methodologies to social involvement, through organizational concerns and technologies. Challenging the perception of learning as knowledge transfer, we introduce a 'Uses, Practices & Strategies' model operationalized by the 'Immersive Learning Brain' and ‘Immersion Cube’ frameworks. This approach offers a comprehensive guide through the intricacies of immersive educational experiences and spotlighting research frontiers, along the immersion dimensions of system, narrative, and agency. Our discourse extends to stakeholders beyond the academic sphere, addressing the interests of technologists, instructional designers, and policymakers. We span various contexts, from formal education to organizational transformation to the new horizon of an AI-pervasive society. This keynote aims to unite the iLRN community in a collaborative journey towards a future where immersive learning research and practice coalesce, paving the way for innovative educational research and practice landscapes.
The debris of the ‘last major merger’ is dynamically youngSérgio Sacani
The Milky Way’s (MW) inner stellar halo contains an [Fe/H]-rich component with highly eccentric orbits, often referred to as the
‘last major merger.’ Hypotheses for the origin of this component include Gaia-Sausage/Enceladus (GSE), where the progenitor
collided with the MW proto-disc 8–11 Gyr ago, and the Virgo Radial Merger (VRM), where the progenitor collided with the
MW disc within the last 3 Gyr. These two scenarios make different predictions about observable structure in local phase space,
because the morphology of debris depends on how long it has had to phase mix. The recently identified phase-space folds in Gaia
DR3 have positive caustic velocities, making them fundamentally different than the phase-mixed chevrons found in simulations
at late times. Roughly 20 per cent of the stars in the prograde local stellar halo are associated with the observed caustics. Based
on a simple phase-mixing model, the observed number of caustics are consistent with a merger that occurred 1–2 Gyr ago.
We also compare the observed phase-space distribution to FIRE-2 Latte simulations of GSE-like mergers, using a quantitative
measurement of phase mixing (2D causticality). The observed local phase-space distribution best matches the simulated data
1–2 Gyr after collision, and certainly not later than 3 Gyr. This is further evidence that the progenitor of the ‘last major merger’
did not collide with the MW proto-disc at early times, as is thought for the GSE, but instead collided with the MW disc within
the last few Gyr, consistent with the body of work surrounding the VRM.
Travis Hills' Endeavors in Minnesota: Fostering Environmental and Economic Pr...Travis Hills MN
Travis Hills of Minnesota developed a method to convert waste into high-value dry fertilizer, significantly enriching soil quality. By providing farmers with a valuable resource derived from waste, Travis Hills helps enhance farm profitability while promoting environmental stewardship. Travis Hills' sustainable practices lead to cost savings and increased revenue for farmers by improving resource efficiency and reducing waste.
Phenomics assisted breeding in crop improvementIshaGoswami9
As the population is increasing and will reach about 9 billion upto 2050. Also due to climate change, it is difficult to meet the food requirement of such a large population. Facing the challenges presented by resource shortages, climate
change, and increasing global population, crop yield and quality need to be improved in a sustainable way over the coming decades. Genetic improvement by breeding is the best way to increase crop productivity. With the rapid progression of functional
genomics, an increasing number of crop genomes have been sequenced and dozens of genes influencing key agronomic traits have been identified. However, current genome sequence information has not been adequately exploited for understanding
the complex characteristics of multiple gene, owing to a lack of crop phenotypic data. Efficient, automatic, and accurate technologies and platforms that can capture phenotypic data that can
be linked to genomics information for crop improvement at all growth stages have become as important as genotyping. Thus,
high-throughput phenotyping has become the major bottleneck restricting crop breeding. Plant phenomics has been defined as the high-throughput, accurate acquisition and analysis of multi-dimensional phenotypes
during crop growing stages at the organism level, including the cell, tissue, organ, individual plant, plot, and field levels. With the rapid development of novel sensors, imaging technology,
and analysis methods, numerous infrastructure platforms have been developed for phenotyping.
Current Ms word generated power point presentation covers major details about the micronuclei test. It's significance and assays to conduct it. It is used to detect the micronuclei formation inside the cells of nearly every multicellular organism. It's formation takes place during chromosomal sepration at metaphase.
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.