This document provides an overview of junction field-effect transistors (JFETs), including their basic construction and operation. It develops analytic equations to model JFET behavior, such as equations for drain current, transconductance gain, and normalized parameters. It also compares approximate and more exact mathematical models for JFETs, showing that the approximate model is reasonably accurate while being more convenient.
This document provides an overview of the Junction Field Effect Transistor (JFET). It discusses the construction of JFETs including the source, drain and gate terminals. It describes the theory of operation explaining how applying voltages to the gate can control the channel and current flow. The key sections outline the characteristic I-V curve, pinch-off voltage, saturation level and cut-off voltage. Advantages of JFETs are also summarized such as high input impedance. Common applications are listed including use as amplifiers and constant current sources.
This document discusses field effect transistors (FETs) and provides details about junction FETs (JFETs). It describes the basic structure and operation of N-channel and P-channel JFETs. Key points covered include:
- FETs are voltage-controlled, unipolar devices that come in two main types: JFETs and MOSFETs.
- A JFET has two P-type regions diffused into an N-type (N-channel JFET) or two N-type regions into a P-type (P-channel JFET) material to form a channel. Applying a voltage to the gate controls the channel.
- The characteristics of a
The document discusses different types of field effect transistors (FETs), including:
1) Junction FETs (JFETs), which operate in depletion mode only and have a non-linear relationship between input voltage and output current.
2) Depletion-mode metal-oxide-semiconductor FETs (D-MOSFETs), which can operate in either depletion or enhancement mode.
3) Enhancement-mode MOSFETs (E-MOSFETs), which only operate in enhancement mode and have an output current of zero until the input voltage exceeds the threshold voltage.
The document provides an overview of field effect transistors (FETs), including the junction FET (JFET) and metal-oxide-semiconductor FET (MOSFET). It discusses the basic structure and operation of n-channel JFETs, including how the gate-source voltage controls the channel width and thus the drain current. Key JFET parameters like pinch-off voltage, cutoff voltage, and transfer characteristics are explained. Methods of biasing JFETs like self-bias and voltage divider bias are also covered. Finally, the document introduces MOSFETs and distinguishes between depletion and enhancement MOSFET types.
FIELD EFFECT TRANSISTERS (FET)
Types of Field Effect Transistors
i) Junction field effect transistor (JFET)
(ii) Metal oxide semiconductor field effect transistor (MOSFET)
Introduction to Junction Field Effect TransistorVARUN KUMAR
This document provides an introduction to JFETs (junction field effect transistors). It defines key terms like source, drain, gate, and channel. It explains that JFETs are voltage-controlled, unipolar devices and discusses n-channel and p-channel JFET operation. The document also derives the mathematical expression for pinch-off voltage and defines the ohmic, saturation, and breakdown regions of the JFET voltage-ampere characteristics.
Field Effect Transistors (FETs) are voltage-controlled three-terminal devices that conduct current through an electric field. There are two types of FETs: JFETs and MOSFETs. JFETs conduct current through a channel using only one type of carrier. MOSFETs became more popular than JFETs due to their smaller size and simpler manufacturing process. Complementary MOS (CMOS) circuits combine both PMOS and NMOS transistors for more powerful circuit design possibilities.
The document discusses different types of field effect transistors (FETs), including JFETs and MOSFETs. It explains the construction, operation, and characteristics of n-channel JFETs and describes how to plot their transfer and drain characteristics. It also covers depletion-type and enhancement-type MOSFETs, discussing their construction, modes of operation, and how to plot their transfer curves. Key aspects like threshold voltage and methods of testing FETs are also summarized.
This document provides an overview of the Junction Field Effect Transistor (JFET). It discusses the construction of JFETs including the source, drain and gate terminals. It describes the theory of operation explaining how applying voltages to the gate can control the channel and current flow. The key sections outline the characteristic I-V curve, pinch-off voltage, saturation level and cut-off voltage. Advantages of JFETs are also summarized such as high input impedance. Common applications are listed including use as amplifiers and constant current sources.
This document discusses field effect transistors (FETs) and provides details about junction FETs (JFETs). It describes the basic structure and operation of N-channel and P-channel JFETs. Key points covered include:
- FETs are voltage-controlled, unipolar devices that come in two main types: JFETs and MOSFETs.
- A JFET has two P-type regions diffused into an N-type (N-channel JFET) or two N-type regions into a P-type (P-channel JFET) material to form a channel. Applying a voltage to the gate controls the channel.
- The characteristics of a
The document discusses different types of field effect transistors (FETs), including:
1) Junction FETs (JFETs), which operate in depletion mode only and have a non-linear relationship between input voltage and output current.
2) Depletion-mode metal-oxide-semiconductor FETs (D-MOSFETs), which can operate in either depletion or enhancement mode.
3) Enhancement-mode MOSFETs (E-MOSFETs), which only operate in enhancement mode and have an output current of zero until the input voltage exceeds the threshold voltage.
The document provides an overview of field effect transistors (FETs), including the junction FET (JFET) and metal-oxide-semiconductor FET (MOSFET). It discusses the basic structure and operation of n-channel JFETs, including how the gate-source voltage controls the channel width and thus the drain current. Key JFET parameters like pinch-off voltage, cutoff voltage, and transfer characteristics are explained. Methods of biasing JFETs like self-bias and voltage divider bias are also covered. Finally, the document introduces MOSFETs and distinguishes between depletion and enhancement MOSFET types.
FIELD EFFECT TRANSISTERS (FET)
Types of Field Effect Transistors
i) Junction field effect transistor (JFET)
(ii) Metal oxide semiconductor field effect transistor (MOSFET)
Introduction to Junction Field Effect TransistorVARUN KUMAR
This document provides an introduction to JFETs (junction field effect transistors). It defines key terms like source, drain, gate, and channel. It explains that JFETs are voltage-controlled, unipolar devices and discusses n-channel and p-channel JFET operation. The document also derives the mathematical expression for pinch-off voltage and defines the ohmic, saturation, and breakdown regions of the JFET voltage-ampere characteristics.
Field Effect Transistors (FETs) are voltage-controlled three-terminal devices that conduct current through an electric field. There are two types of FETs: JFETs and MOSFETs. JFETs conduct current through a channel using only one type of carrier. MOSFETs became more popular than JFETs due to their smaller size and simpler manufacturing process. Complementary MOS (CMOS) circuits combine both PMOS and NMOS transistors for more powerful circuit design possibilities.
The document discusses different types of field effect transistors (FETs), including JFETs and MOSFETs. It explains the construction, operation, and characteristics of n-channel JFETs and describes how to plot their transfer and drain characteristics. It also covers depletion-type and enhancement-type MOSFETs, discussing their construction, modes of operation, and how to plot their transfer curves. Key aspects like threshold voltage and methods of testing FETs are also summarized.
This document discusses field-effect transistors (FETs), specifically the junction field-effect transistor (JFET) and metal-oxide-semiconductor field-effect transistor (MOSFET). It describes the construction and operation of the n-channel JFET, including how applying a voltage to the gate controls the width of the depletion region and thus the current flowing between the source and drain terminals. The document also compares key differences between FETs and bipolar junction transistors (BJTs), such as FETs being unipolar devices with higher input impedance and thermal stability.
This document discusses the Junction Field Effect Transistor (JFET). It provides an introduction, explaining that a JFET is a three-terminal semiconductor device that can be used as a controlled switch, amplifier, or voltage-controlled resistor. It operates using the properties of a PN junction diode under forward and reverse bias. The document then discusses the construction of JFETs using diffusion and planar techniques, providing diagrams. It also covers the schematic symbol, polarity convention, and working principle of a JFET, comparing it to squeezing a garden hose to control water flow. Key characteristics and applications are summarized, along with the conclusion that JFETs are unipolar devices widely used as amplifiers with high input
This document discusses field effect transistors (FETs), including JFETs and MOSFETs. It provides figures illustrating the structure and characteristics of an n-channel JFET, including its biasing circuit. The document also shows typical drain characteristics and transfer curves of a JFET.
The document discusses the unijunction transistor (UJT), a three-terminal semiconductor device with one PN junction. It consists of a lightly doped silicon bar with a heavily doped P-type material alloyed to one side, forming the single junction. The UJT has three terminals - an emitter, and two bases B1 and B2. When a voltage is applied across B2-B1, the UJT exhibits a negative resistance characteristic, allowing it to be used as an oscillator. Once triggered by a pulse at one of its terminals, the emitter current increases regeneratively until a limiting value is reached. Applications of the UJT include phase control, switching, pulse generation, and timing circuits.
The document discusses field effect transistors (FETs). It describes two types of FETs: junction FETs (JFETs) and metal-oxide-semiconductor FETs (MOSFETs). A JFET consists of a bar of N-type or P-type semiconductor with P-N junctions on either side, forming the gate. Applying a voltage between the gate and source controls the width of a depletion region, which in turn controls the flow of current from source to drain. FETs have less internal resistance and noise than junction transistors, making them preferable for many applications.
The unijunction transistor (UJT) is a three-terminal semiconductor device with a single PN junction. It exhibits a negative resistance characteristic, which makes it useful for oscillator circuits. The UJT consists of a lightly doped N-type silicon bar with a single P-type region forming the emitter junction. It has three terminals - base 1, base 2, and emitter. In its active mode, the UJT shows negative resistance, where increasing the emitter voltage initially causes the emitter current to decrease. This physical phenomenon is called conductivity modulation and is caused by injection of holes from the emitter into the base, decreasing the resistance between the emitter and base 1.
This document provides an overview of field effect transistors (FETs). It discusses the basic construction and operating principles of FETs, including that they are three-terminal devices that use an electric field to control current between the source and drain terminals. The document outlines different types of FETs such as JFETs, MOSFETs, and describes the construction and operating characteristics of n-channel and p-channel JFETs as well as depletion and enhancement mode MOSFETs. It provides details on how applying voltage at the gate terminal controls the width of the current-carrying channel and thus the current between the source and drain.
There are two types of JFET transistors - n-channel and p-channel. The document discusses the characteristics and operation of both types. It also covers various applications of JFETs such as amplifiers, constant current sources, and analog switches. The different classes of amplifiers - Class A, B, AB, and C - are described based on how much of the input signal cycle the output device conducts. Load lines are also discussed as a way to represent the operating points of a transistor on its output characteristics curve.
The three terminals of the FET are known as Gate, Drain, and Source.
It is a voltage controlled device, where the input voltage controls by the output current.
In FET current used to flow between the drain and the source terminal. And this current can be controlled by applying the voltage between the gate and the source terminal.
So this applied voltage generate the electric field within the device and by controlling these electric field we can control the flow of current through the device.
The document discusses Field Effect Transistors (FETs). It begins by defining some key characteristics of FETs, including that they are unipolar devices controlled by voltage and have very high input impedance. It then describes different types of FETs, including JFETs, MOSFETs, and discusses their characteristics such as transfer curves. The document provides examples of biasing circuits used for FETs and analyzing FET amplifiers at mid-frequency.
A field-effect transistor (FET) uses an electric field to control the width of a channel in a semiconductor, thereby varying its current-carrying ability. The most common types are metal-oxide-semiconductor FETs (MOSFETs) and junction gate FETs (JFETs). An n-channel enhancement-mode MOSFET (NMOS) is described, where applying a voltage between the gate and source forms an n-type channel. In the ohmic region, the NMOS acts as a voltage-controlled resistor, while in the saturation region the channel is pinched off and current no longer changes with drain-source voltage. Key equations relate the three terminal voltages and currents in
EC8452 Electronic Circuits II - UJT Relaxation Oscillatorchitrarengasamy
This document describes the physical structure and operation of a unijunction transistor (UJT). It consists of a lightly doped N-type silicon slab with base contacts at each end and a p-type aluminum rod alloyed into the slab closer to one base. The equivalent circuit includes two resistors (one fixed, one variable) and a diode. When the emitter voltage exceeds the firing potential, current flows and the device enters a negative resistance region, allowing it to be used in relaxation oscillators to generate oscillating signals.
- The JFET is a voltage-controlled device that uses an electric field to control the flow of current. It has three terminals: the drain, gate, and source.
- There are two types of JFETs: n-channel and p-channel. In an n-channel JFET, applying a negative voltage to the gate reduces the channel width and thereby the current between the drain and source. In a p-channel JFET the behavior is opposite.
- The JFET characteristics show the drain current (ID) as a function of drain-source voltage (VDS) for different gate-source voltages (VGS). ID increases with VDS until reaching pinch-off, then becomes constant.
The document discusses field effect transistors (FETs), specifically junction field effect transistors (JFETs) and metal-oxide-semiconductor field effect transistors (MOSFETs). It describes the basic construction, operation, and characteristics of n-channel and p-channel JFETs and MOSFETs. Application circuits for JFET and MOSFET amplifiers and switches are also presented. Key differences between BJTs, JFETs, and MOSFETs are highlighted.
Biasing is the process of applying external voltages to transistors to ensure proper operation. It involves forward or reverse biasing transistor junctions to place the device in specific regions like active, saturation, or cutoff. Common biasing circuits include fixed bias using a base resistor, collector-to-base bias which provides feedback, and emitter bias where a resistor is added to stabilize operating point. Proper biasing establishes a quiescent point and load line on the transistor characteristics curve for linear amplification.
The document summarizes different types of field-effect transistors (FETs). It describes the invention of the transistor in 1947 and its impact. It then discusses the basic principles and constructions of junction FETs (JFETs), metal-oxide-semiconductor FETs (MOSFETs) including n-channel and p-channel enhancement and depletion mode MOSFETs. Key differences between FETs, BJTs, and operating characteristics such as different regions of operation are also summarized. The document provides a high-level overview of various FET technologies.
This document discusses field effect transistors (FETs). It defines FETs and describes their basic working mechanisms, including junction FETs (JFETs) and metal-oxide-semiconductor FETs (MOSFETs). The document also covers biasing circuits for FET amplifiers, types of FETs such as enhancement and depletion mode MOSFETs, and applications of FETs such as in analog switches and amplifiers.
Field-effect transistor amplifiers provide an excellent voltage gain with the added feature of high input impedance. They are also low-power-consumption configurations with good frequency range and minimal size and weight.
JFETs, depletion MOSFETs, and MESFETs can be used to design amplifiers having similar voltage gains.
The depletion MOSFET (MESFET) circuit, however, has a much higher input impedance than a similar JFET configuration.
The document discusses the programmable unijunction transistor (PUT). It begins by explaining that the PUT consists of 4 layers like a thyristor, with connections to the first, last, and inner layers as the anode, cathode, and gate. PUTs require an external resistor network to set the intrinsic standoff ratio η, similarly to how external resistors program unijunction transistors. The document then covers the basic operation and characteristic curves of PUTs, which resemble those of unijunction transistors. It presents an example PUT relaxation oscillator circuit and discusses design considerations for the charging resistor values.
This document discusses field effect transistors (FETs). It provides an introduction to FETs, describing their basic structure and operation. It discusses the different types of FETs including JFETs and MOSFETs. It describes the terminals (gate, source, drain) of FETs and how a voltage applied to the gate controls the flow of current between the source and drain. It also outlines some key advantages and disadvantages of FETs compared to other transistors.
Field-effect transistors (FETs) are voltage-controlled semiconductor devices that rely on an electric field to control the shape and conductivity of a channel in the semiconductor material. The basic principle of FETs involves three terminals - the gate, source, and drain - where a voltage applied to the gate controls the current flow between the source and drain terminals. There are two main types of FETs: junction FETs (JFETs) which have a doped semiconductor channel, and metal-oxide-semiconductor FETs (MOSFETs) which use a metal gate separated from the channel by an oxide layer. FETs can be used for switching, amplifying signals, and as variable resistors
This document discusses field-effect transistors (FETs), specifically the junction field-effect transistor (JFET) and metal-oxide-semiconductor field-effect transistor (MOSFET). It describes the construction and operation of the n-channel JFET, including how applying a voltage to the gate controls the width of the depletion region and thus the current flowing between the source and drain terminals. The document also compares key differences between FETs and bipolar junction transistors (BJTs), such as FETs being unipolar devices with higher input impedance and thermal stability.
This document discusses the Junction Field Effect Transistor (JFET). It provides an introduction, explaining that a JFET is a three-terminal semiconductor device that can be used as a controlled switch, amplifier, or voltage-controlled resistor. It operates using the properties of a PN junction diode under forward and reverse bias. The document then discusses the construction of JFETs using diffusion and planar techniques, providing diagrams. It also covers the schematic symbol, polarity convention, and working principle of a JFET, comparing it to squeezing a garden hose to control water flow. Key characteristics and applications are summarized, along with the conclusion that JFETs are unipolar devices widely used as amplifiers with high input
This document discusses field effect transistors (FETs), including JFETs and MOSFETs. It provides figures illustrating the structure and characteristics of an n-channel JFET, including its biasing circuit. The document also shows typical drain characteristics and transfer curves of a JFET.
The document discusses the unijunction transistor (UJT), a three-terminal semiconductor device with one PN junction. It consists of a lightly doped silicon bar with a heavily doped P-type material alloyed to one side, forming the single junction. The UJT has three terminals - an emitter, and two bases B1 and B2. When a voltage is applied across B2-B1, the UJT exhibits a negative resistance characteristic, allowing it to be used as an oscillator. Once triggered by a pulse at one of its terminals, the emitter current increases regeneratively until a limiting value is reached. Applications of the UJT include phase control, switching, pulse generation, and timing circuits.
The document discusses field effect transistors (FETs). It describes two types of FETs: junction FETs (JFETs) and metal-oxide-semiconductor FETs (MOSFETs). A JFET consists of a bar of N-type or P-type semiconductor with P-N junctions on either side, forming the gate. Applying a voltage between the gate and source controls the width of a depletion region, which in turn controls the flow of current from source to drain. FETs have less internal resistance and noise than junction transistors, making them preferable for many applications.
The unijunction transistor (UJT) is a three-terminal semiconductor device with a single PN junction. It exhibits a negative resistance characteristic, which makes it useful for oscillator circuits. The UJT consists of a lightly doped N-type silicon bar with a single P-type region forming the emitter junction. It has three terminals - base 1, base 2, and emitter. In its active mode, the UJT shows negative resistance, where increasing the emitter voltage initially causes the emitter current to decrease. This physical phenomenon is called conductivity modulation and is caused by injection of holes from the emitter into the base, decreasing the resistance between the emitter and base 1.
This document provides an overview of field effect transistors (FETs). It discusses the basic construction and operating principles of FETs, including that they are three-terminal devices that use an electric field to control current between the source and drain terminals. The document outlines different types of FETs such as JFETs, MOSFETs, and describes the construction and operating characteristics of n-channel and p-channel JFETs as well as depletion and enhancement mode MOSFETs. It provides details on how applying voltage at the gate terminal controls the width of the current-carrying channel and thus the current between the source and drain.
There are two types of JFET transistors - n-channel and p-channel. The document discusses the characteristics and operation of both types. It also covers various applications of JFETs such as amplifiers, constant current sources, and analog switches. The different classes of amplifiers - Class A, B, AB, and C - are described based on how much of the input signal cycle the output device conducts. Load lines are also discussed as a way to represent the operating points of a transistor on its output characteristics curve.
The three terminals of the FET are known as Gate, Drain, and Source.
It is a voltage controlled device, where the input voltage controls by the output current.
In FET current used to flow between the drain and the source terminal. And this current can be controlled by applying the voltage between the gate and the source terminal.
So this applied voltage generate the electric field within the device and by controlling these electric field we can control the flow of current through the device.
The document discusses Field Effect Transistors (FETs). It begins by defining some key characteristics of FETs, including that they are unipolar devices controlled by voltage and have very high input impedance. It then describes different types of FETs, including JFETs, MOSFETs, and discusses their characteristics such as transfer curves. The document provides examples of biasing circuits used for FETs and analyzing FET amplifiers at mid-frequency.
A field-effect transistor (FET) uses an electric field to control the width of a channel in a semiconductor, thereby varying its current-carrying ability. The most common types are metal-oxide-semiconductor FETs (MOSFETs) and junction gate FETs (JFETs). An n-channel enhancement-mode MOSFET (NMOS) is described, where applying a voltage between the gate and source forms an n-type channel. In the ohmic region, the NMOS acts as a voltage-controlled resistor, while in the saturation region the channel is pinched off and current no longer changes with drain-source voltage. Key equations relate the three terminal voltages and currents in
EC8452 Electronic Circuits II - UJT Relaxation Oscillatorchitrarengasamy
This document describes the physical structure and operation of a unijunction transistor (UJT). It consists of a lightly doped N-type silicon slab with base contacts at each end and a p-type aluminum rod alloyed into the slab closer to one base. The equivalent circuit includes two resistors (one fixed, one variable) and a diode. When the emitter voltage exceeds the firing potential, current flows and the device enters a negative resistance region, allowing it to be used in relaxation oscillators to generate oscillating signals.
- The JFET is a voltage-controlled device that uses an electric field to control the flow of current. It has three terminals: the drain, gate, and source.
- There are two types of JFETs: n-channel and p-channel. In an n-channel JFET, applying a negative voltage to the gate reduces the channel width and thereby the current between the drain and source. In a p-channel JFET the behavior is opposite.
- The JFET characteristics show the drain current (ID) as a function of drain-source voltage (VDS) for different gate-source voltages (VGS). ID increases with VDS until reaching pinch-off, then becomes constant.
The document discusses field effect transistors (FETs), specifically junction field effect transistors (JFETs) and metal-oxide-semiconductor field effect transistors (MOSFETs). It describes the basic construction, operation, and characteristics of n-channel and p-channel JFETs and MOSFETs. Application circuits for JFET and MOSFET amplifiers and switches are also presented. Key differences between BJTs, JFETs, and MOSFETs are highlighted.
Biasing is the process of applying external voltages to transistors to ensure proper operation. It involves forward or reverse biasing transistor junctions to place the device in specific regions like active, saturation, or cutoff. Common biasing circuits include fixed bias using a base resistor, collector-to-base bias which provides feedback, and emitter bias where a resistor is added to stabilize operating point. Proper biasing establishes a quiescent point and load line on the transistor characteristics curve for linear amplification.
The document summarizes different types of field-effect transistors (FETs). It describes the invention of the transistor in 1947 and its impact. It then discusses the basic principles and constructions of junction FETs (JFETs), metal-oxide-semiconductor FETs (MOSFETs) including n-channel and p-channel enhancement and depletion mode MOSFETs. Key differences between FETs, BJTs, and operating characteristics such as different regions of operation are also summarized. The document provides a high-level overview of various FET technologies.
This document discusses field effect transistors (FETs). It defines FETs and describes their basic working mechanisms, including junction FETs (JFETs) and metal-oxide-semiconductor FETs (MOSFETs). The document also covers biasing circuits for FET amplifiers, types of FETs such as enhancement and depletion mode MOSFETs, and applications of FETs such as in analog switches and amplifiers.
Field-effect transistor amplifiers provide an excellent voltage gain with the added feature of high input impedance. They are also low-power-consumption configurations with good frequency range and minimal size and weight.
JFETs, depletion MOSFETs, and MESFETs can be used to design amplifiers having similar voltage gains.
The depletion MOSFET (MESFET) circuit, however, has a much higher input impedance than a similar JFET configuration.
The document discusses the programmable unijunction transistor (PUT). It begins by explaining that the PUT consists of 4 layers like a thyristor, with connections to the first, last, and inner layers as the anode, cathode, and gate. PUTs require an external resistor network to set the intrinsic standoff ratio η, similarly to how external resistors program unijunction transistors. The document then covers the basic operation and characteristic curves of PUTs, which resemble those of unijunction transistors. It presents an example PUT relaxation oscillator circuit and discusses design considerations for the charging resistor values.
This document discusses field effect transistors (FETs). It provides an introduction to FETs, describing their basic structure and operation. It discusses the different types of FETs including JFETs and MOSFETs. It describes the terminals (gate, source, drain) of FETs and how a voltage applied to the gate controls the flow of current between the source and drain. It also outlines some key advantages and disadvantages of FETs compared to other transistors.
Field-effect transistors (FETs) are voltage-controlled semiconductor devices that rely on an electric field to control the shape and conductivity of a channel in the semiconductor material. The basic principle of FETs involves three terminals - the gate, source, and drain - where a voltage applied to the gate controls the current flow between the source and drain terminals. There are two main types of FETs: junction FETs (JFETs) which have a doped semiconductor channel, and metal-oxide-semiconductor FETs (MOSFETs) which use a metal gate separated from the channel by an oxide layer. FETs can be used for switching, amplifying signals, and as variable resistors
The document discusses different types of field effect transistors (FETs), including junction FETs (JFETs), metal-oxide-semiconductor FETs (MOSFETs), and metal-semiconductor FETs (MESFETs). It focuses on the structure and operation of n-channel and p-channel MOSFETs, describing how a positive or negative gate voltage is used to create a conducting channel. Scaling challenges for MOSFETs are also discussed, along with new materials needed like high-k dielectrics and metal gates, and approaches like silicon-on-insulator (SOI) technology.
This document provides an introduction to field effect transistors (FETs) and the junction field effect transistor (JFET) in particular. It discusses the key differences between JFETs and bipolar junction transistors (BJTs), including that JFETs are unipolar devices that operate with only one type of charge carrier and are voltage-controlled rather than current-controlled. The document then describes the structure and operation of JFETs, including the use of reverse biasing the gate-source junction to control current flow. It provides examples of calculating important JFET parameters and biasing JFETs in common configurations like self-bias and voltage divider bias.
A MOSFET (Metal Oxide Semiconductor Field Effect Transistor) is a semiconductor device that is commonly used in power electronics. It works by modulating charge concentration between a gate electrode, which is insulated from other device regions by an oxide layer, and a body region. Depending on whether it is an n-channel or p-channel MOSFET, the source and drain regions have either n+ or p+ doping while the body has the opposite doping. Applying a voltage to the gate can turn the channel between source and drain on or off to allow or prevent current flow. MOSFETs can be made with silicon on insulator or other semiconductor materials.
This document discusses MOSFETs and JFETs. It introduces MOSFETs, describing the metal oxide layer and how the electric field controls current. It describes types of MOSFETs and their applications, particularly as switches. Characteristic curves of MOSFETs are also mentioned. The document then introduces JFETs, describing their structure and operation. Applications of JFETs as switches are provided. Advantages and disadvantages of JFETs are listed. Finally, characteristics curves of JFETs, including output and transfer characteristics, are described.
Presentation on bipolar junction transistorKawsar Ahmed
This presentation introduces bipolar junction transistors (BJTs). It discusses the two types of BJTs - NPN and PNP transistors, which differ based on whether holes or electrons are the majority carriers. The key components of a transistor - emitter, base, and collector - are defined. The presentation compares the three common transistor configurations - common base, common emitter, and common collector - and provides expressions for collector current in each. It also discusses transistor operation, characteristics, and applications such as amplification. Overall, the presentation provides a comprehensive overview of BJT fundamentals.
The document discusses the zener diode, how it works, its applications, and use in voltage regulation. A zener diode allows current to flow in both directions, maintaining a nearly constant voltage when the reverse breakdown voltage is exceeded. It is commonly used to provide a stable reference voltage for power supplies and other equipment requiring voltage regulation. The zener diode's impedance adjusts to varying input voltages and loads to regulate its designated voltage within a specified operating current range.
The document is a presentation on silicon controlled rectifiers (SCRs) given by five students. It introduces SCRs, explaining that they are power electronic devices that can convert AC to DC and control power to a load. The presentation describes the basic structure and operation of SCRs, including how applying a voltage to the gate terminal allows current to flow. It also covers the characteristics curve and applications of SCRs in areas like rectification, power supplies, motor controls and battery charging. In conclusion, SCRs are widely used power components due to their ability to easily switch high currents and their low cost.
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.
The document discusses the silicon controlled rectifier (SCR), a three-terminal semiconductor device that acts as a controlled switch. It can rectify AC to DC and control the amount of power delivered to a load. The SCR combines the functions of a rectifier and transistor. Key points include:
1) An SCR has two states - it either does not conduct or conducts heavily, behaving like a switch.
2) It is turned on by applying a small positive voltage to the gate, as the breakover voltage is usually much higher than the supply voltage.
3) To turn it off, the supply voltage must be reduced to zero to stop conduction.
This document provides an introduction to transistors and MOSFETs. It begins by describing the invention of the transistor in 1947 and defining what a transistor is. It then discusses the main types of transistors - BJT and FET, including MOSFET and JFET. The rest of the document focuses on MOSFETs, explaining what they are, their terminals and symbols, types of MOSFETs like n-MOSFET and p-MOSFET, and how MOSFETs work and are fabricated through processes like photolithography, etching, diffusion, and oxidation. It includes diagrams of MOSFET structure and operation. In the end it briefly discusses CMOS fabrication process flow.
Bipolar junction transistors (BJTs) are three-terminal semiconductor devices consisting of two pn junctions. There are two types, NPN and PNP, depending on the order of doping. BJTs can operate as amplifiers and switches by controlling the flow of majority charge carriers through the base terminal. Proper biasing is required to operate the transistor in its active region between cutoff and saturation. Common configurations include common-base, common-emitter, and common-collector, each with different input and output characteristics. Maximum ratings like power dissipation and voltages must be considered for circuit design and temperature derating.
A MOSFET is a semiconductor device that can amplify or switch electronic signals. It has three terminals - drain, source, and gate. Depending on whether the semiconductor material between the drain and source is n-type or p-type, a MOSFET can be an n-channel or p-channel type. Applying a positive voltage to the gate of an n-channel MOSFET or a negative voltage to the gate of a p-channel MOSFET allows current to flow between the drain and source. MOSFETs are commonly used as switches in digital circuits like processors and as amplifiers in analog circuits. They are also used in memory devices, power supplies, and other electronic applications.
FETs are three-terminal transistors that control the flow of electrons or electron holes through a channel between the source and drain terminals. There are two types - n-channel and p-channel - depending on if the channel is doped to be n-type or p-type semiconductor. Different types of FETs include JFETs, MOSFETs, IGBTs, and many others that use different materials and structures. FETs are widely used in digital circuits, analog signal switching and amplification, and applications requiring fast switching such as engine ignition coils.
The document discusses analog circuit design and transistor behavior at high frequencies. It covers transistor models at high frequency, the Miller Effect, amplifiers' frequency response, and practical considerations for using simplified transistor models. Diagrams are included showing high-frequency transistor equivalent circuits and how feedback impedances can be modeled as parallel impedances at the input and output terminals, known as the Miller Effect approximation.
SPICE MODEL of 1SS193 (Standard Model) in SPICE PARKTsuyoshi Horigome
This document summarizes the component modeling report for a Toshiba 1SS193 general purpose rectifier diode. It includes:
1) Details of the diode part number and manufacturer.
2) Descriptions of the diode circuit configuration and SPICE model parameters.
3) Simulation results and comparisons to measurements for the diode's forward and reverse characteristics, including current, capacitance, and recovery time.
4) Conclusions that the SPICE model accurately simulates the diode's performance within 1% error or better.
SPICE MODEL of 1SS193 (Standard Model) in SPICE PARKTsuyoshi Horigome
SPICE MODEL of 1SS193 (Standard Model) in SPICE PARK. English Version is http://www.spicepark.net.Japanese Version is http://www.spicepark.com by Bee Technologies.
SPICE MODEL of SSM3J120TU (Professional+BDP Model) in SPICE PARKTsuyoshi Horigome
SPICE MODEL of SSM3J120TU (Professional+BDP Model) in SPICE PARK. English Version is http://www.spicepark.net. Japanese Version is http://www.spicepark.com by Bee Technologies.
SPICE MODEL of SSM3J15FS (Professional+BDP Model) in SPICE PARKTsuyoshi Horigome
This document summarizes the modeling and simulation of a Power MOSFET component. It includes:
1) Details of the MOSFET model used in the simulation including parameters like channel length, threshold voltage, resistances, and more.
2) Simulation results graphs comparing measurements to simulations of characteristics like transconductance, Id-Vgs, Rds(on), capacitances, switching times and more.
3) Circuit diagrams showing the simulation setup for evaluating each characteristic.
4) Tables comparing measurement and simulation values with percent error calculations.
The document provides a thorough characterization of the modeled MOSFET component through electrical simulation and evaluation against real measurements.
This document summarizes the specifications and simulation results for a 1SS187 general purpose rectifier diode made by Toshiba. It includes the diode's SPICE model parameters, forward and reverse characteristics from circuit simulations, and comparison of simulated and measured results showing close matches. Reverse recovery time was simulated as 6.97ns compared to a measured 7ns.
SPICE MODEL of DF2B6.8FS , PSpice Model in SPICE PARKTsuyoshi Horigome
SPICE MODEL of DF2B6.8FS , PSpice Model in SPICE PARK. English Version is http://www.spicepark.net. Japanese Version is http://www.spicepark.com by Bee Technologies.
SPICE MODEL of SSM3J15FS (Standard+BDS Model) in SPICE PARKTsuyoshi Horigome
SPICE MODEL of SSM3J15FS (Standard+BDS) in SPICE PARK. English Version is http://www.spicepark.net. Japanese Version is http://www.spicepark.com by Bee Technologies.
SPICE MODEL of 1SS193 (Professional Model) in SPICE PARKTsuyoshi Horigome
SPICE MODEL of 1SS193 (Professional Model) in SPICE PARK. English Version is http://www.spicepark.net. Japanese Version is http://www.spicepark.com by Bee Technologies.
SPICE MODEL of SSM3J115TU (Professional+BDP Model) in SPICE PARKTsuyoshi Horigome
SPICE MODEL of SSM3J115TU (Professional+BDP Model) in SPICE PARK. English Version is http://www.spicepark.net. Japanese Version is http://www.spicepark.com by Bee Technologies.
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SPICE MODEL of 1SS184 (Standard Model) in SPICE PARK. English Version is http://www.spicepark.net.Japanese Version is http://www.spicepark.com by Bee Technologies.
SPICE MODEL of 1SS184 (Standard Model) in SPICE PARKTsuyoshi Horigome
SPICE MODEL of 1SS184 (Standard Model) in SPICE PARK. English Version is http://www.spicepark.net.Japanese Version is http://www.spicepark.com by Bee Technologies.
SPICE MODEL of 1SS187 (Professional Model) in SPICE PARKTsuyoshi Horigome
SPICE MODEL of 1SS187 (Professional Model) in SPICE PARK. English Version is http://www.spicepark.net. Japanese Version is http://www.spicepark.com by Bee Technologies.
SPICE MODEL of SSM3K102TU (Standard+BDS Model) in SPICE PARKTsuyoshi Horigome
SPICE MODEL of SSM3K102TU (Standard+BDS) in SPICE PARK. English Version is http://www.spicepark.net. Japanese Version is http://www.spicepark.com by Bee Technologies.
SPICE MODEL of MTM23223 (Professional+BDP Model) in SPICE PARKTsuyoshi Horigome
SPICE MODEL of MTM23223 (Professional+BDP Model) in SPICE PARK. English Version is http://www.spicepark.net. Japanese Version is http://www.spicepark.com by Bee Technologies.
SPICE MODEL of 2SJ511 (Standard+BDS Model) in SPICE PARKTsuyoshi Horigome
SPICE MODEL of 2SJ511 (Standard+BDS) in SPICE PARK. English Version is http://www.spicepark.net. Japanese Version is http://www.spicepark.com by Bee Technologies.
SPICE MODEL of MA4S111 (Standard Model) in SPICE PARKTsuyoshi Horigome
This document summarizes the modeling of a Panasonic MA4S111 general purpose diode. It includes:
1) Details of the diode components and part number.
2) Descriptions of the diode model parameters in PSpice software.
3) Simulation results of the diode's forward and reverse characteristics compared to measurements.
4) The diode junction capacitance characteristic from simulation.
5) Reverse recovery time characteristics from simulation and measurement.
SPICE MODEL of MA4S111 (Standard Model) in SPICE PARKTsuyoshi Horigome
SPICE MODEL of MA4S111 (Standard Model) in SPICE PARK. English Version is http://www.spicepark.net.Japanese Version is http://www.spicepark.com by Bee Technologies.
SPICE MODEL of 2SJ511 (Professional+BDP Model) in SPICE PARKTsuyoshi Horigome
This document provides a device modeling report for a Power MOSFET and includes:
1) Specifications and parameters for the MOSFET SPICE model.
2) Simulation results and comparisons to measurement data for key MOSFET characteristics like transconductance, Vgs-Id, Rds(on), capacitance, switching times and more.
3) Specifications and simulation results for the body diode and ESD protection diode models.
SPICE MODEL of SSM3K16FU (Standard+BDS Model) in SPICE PARKTsuyoshi Horigome
SPICE MODEL of SSM3K16FU (Standard+BDS) in SPICE PARK. English Version is http://www.spicepark.net. Japanese Version is http://www.spicepark.com by Bee Technologies.
SPICE MODEL of SSM3J115TU (Standard+BDS Model) in SPICE PARKTsuyoshi Horigome
SPICE MODEL of SSM3J115TU (Standard+BDS) in SPICE PARK. English Version is http://www.spicepark.net. Japanese Version is http://www.spicepark.com by Bee Technologies.
How to Manage Your Lost Opportunities in Odoo 17 CRMCeline George
Odoo 17 CRM allows us to track why we lose sales opportunities with "Lost Reasons." This helps analyze our sales process and identify areas for improvement. Here's how to configure lost reasons in Odoo 17 CRM
ISO/IEC 27001, ISO/IEC 42001, and GDPR: Best Practices for Implementation and...PECB
Denis is a dynamic and results-driven Chief Information Officer (CIO) with a distinguished career spanning information systems analysis and technical project management. With a proven track record of spearheading the design and delivery of cutting-edge Information Management solutions, he has consistently elevated business operations, streamlined reporting functions, and maximized process efficiency.
Certified as an ISO/IEC 27001: Information Security Management Systems (ISMS) Lead Implementer, Data Protection Officer, and Cyber Risks Analyst, Denis brings a heightened focus on data security, privacy, and cyber resilience to every endeavor.
His expertise extends across a diverse spectrum of reporting, database, and web development applications, underpinned by an exceptional grasp of data storage and virtualization technologies. His proficiency in application testing, database administration, and data cleansing ensures seamless execution of complex projects.
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Date: May 29, 2024
Tags: Information Security, ISO/IEC 27001, ISO/IEC 42001, Artificial Intelligence, GDPR
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LAND USE LAND COVER AND NDVI OF MIRZAPUR DISTRICT, UPRAHUL
This Dissertation explores the particular circumstances of Mirzapur, a region located in the
core of India. Mirzapur, with its varied terrains and abundant biodiversity, offers an optimal
environment for investigating the changes in vegetation cover dynamics. Our study utilizes
advanced technologies such as GIS (Geographic Information Systems) and Remote sensing to
analyze the transformations that have taken place over the course of a decade.
The complex relationship between human activities and the environment has been the focus
of extensive research and worry. As the global community grapples with swift urbanization,
population expansion, and economic progress, the effects on natural ecosystems are becoming
more evident. A crucial element of this impact is the alteration of vegetation cover, which plays a
significant role in maintaining the ecological equilibrium of our planet.Land serves as the foundation for all human activities and provides the necessary materials for
these activities. As the most crucial natural resource, its utilization by humans results in different
'Land uses,' which are determined by both human activities and the physical characteristics of the
land.
The utilization of land is impacted by human needs and environmental factors. In countries
like India, rapid population growth and the emphasis on extensive resource exploitation can lead
to significant land degradation, adversely affecting the region's land cover.
Therefore, human intervention has significantly influenced land use patterns over many
centuries, evolving its structure over time and space. In the present era, these changes have
accelerated due to factors such as agriculture and urbanization. Information regarding land use and
cover is essential for various planning and management tasks related to the Earth's surface,
providing crucial environmental data for scientific, resource management, policy purposes, and
diverse human activities.
Accurate understanding of land use and cover is imperative for the development planning
of any area. Consequently, a wide range of professionals, including earth system scientists, land
and water managers, and urban planners, are interested in obtaining data on land use and cover
changes, conversion trends, and other related patterns. The spatial dimensions of land use and
cover support policymakers and scientists in making well-informed decisions, as alterations in
these patterns indicate shifts in economic and social conditions. Monitoring such changes with the
help of Advanced technologies like Remote Sensing and Geographic Information Systems is
crucial for coordinated efforts across different administrative levels. Advanced technologies like
Remote Sensing and Geographic Information Systems
9
Changes in vegetation cover refer to variations in the distribution, composition, and overall
structure of plant communities across different temporal and spatial scales. These changes can
occur natural.
How to Setup Warehouse & Location in Odoo 17 InventoryCeline George
In this slide, we'll explore how to set up warehouses and locations in Odoo 17 Inventory. This will help us manage our stock effectively, track inventory levels, and streamline warehouse operations.
Leveraging Generative AI to Drive Nonprofit InnovationTechSoup
In this webinar, participants learned how to utilize Generative AI to streamline operations and elevate member engagement. Amazon Web Service experts provided a customer specific use cases and dived into low/no-code tools that are quick and easy to deploy through Amazon Web Service (AWS.)
it describes the bony anatomy including the femoral head , acetabulum, labrum . also discusses the capsule , ligaments . muscle that act on the hip joint and the range of motion are outlined. factors affecting hip joint stability and weight transmission through the joint are summarized.
বাংলাদেশের অর্থনৈতিক সমীক্ষা ২০২৪ [Bangladesh Economic Review 2024 Bangla.pdf] কম্পিউটার , ট্যাব ও স্মার্ট ফোন ভার্সন সহ সম্পূর্ণ বাংলা ই-বুক বা pdf বই " সুচিপত্র ...বুকমার্ক মেনু 🔖 ও হাইপার লিংক মেনু 📝👆 যুক্ত ..
আমাদের সবার জন্য খুব খুব গুরুত্বপূর্ণ একটি বই ..বিসিএস, ব্যাংক, ইউনিভার্সিটি ভর্তি ও যে কোন প্রতিযোগিতা মূলক পরীক্ষার জন্য এর খুব ইম্পরট্যান্ট একটি বিষয় ...তাছাড়া বাংলাদেশের সাম্প্রতিক যে কোন ডাটা বা তথ্য এই বইতে পাবেন ...
তাই একজন নাগরিক হিসাবে এই তথ্য গুলো আপনার জানা প্রয়োজন ...।
বিসিএস ও ব্যাংক এর লিখিত পরীক্ষা ...+এছাড়া মাধ্যমিক ও উচ্চমাধ্যমিকের স্টুডেন্টদের জন্য অনেক কাজে আসবে ...
This presentation was provided by Steph Pollock of The American Psychological Association’s Journals Program, and Damita Snow, of The American Society of Civil Engineers (ASCE), for the initial session of NISO's 2024 Training Series "DEIA in the Scholarly Landscape." Session One: 'Setting Expectations: a DEIA Primer,' was held June 6, 2024.
Traditional Musical Instruments of Arunachal Pradesh and Uttar Pradesh - RAYH...
Jfet basics
1. JFET Basics
by Kenneth A. Kuhn
Nov. 3, 2001, rev. Oct. 30, 2008
Introduction
A junction field-effect transistor (JFET) consists of a semiconducting channel whose
conductance is controlled by an electric field. The terminals at either end of the channel
are called source (S) and drain (D). The control electrode that applies the electric field is
called the gate (G) and is made of the opposite type of semiconductor material than the
channel. Thus, there is a PN junction between the gate and the channel. This PN
junction is always reverse biased in normal operation. Figure 1 shows the basic structure.
Figure 1: JFET construction and conduction channel controlled by depletion zone
JFETs are known as depletion mode devices because the channel conducts with zero bias
voltage applied (i.e. the depletion region has zero width). Applying a reverse bias
increases the width of the depletion region which in turn reduces the conduction of the
channel. This is the basis for making an amplifier. The channel conduction resembles a
resistor for low voltage drops (ohmic region) and becomes a constant current for higher
voltage drops (saturation region). The mathematical models we use are based on the
saturation region and will provide incorrect results if used in the ohmic region. The
model for a field effect transistor is a voltage controlled current source. Many JFETs are
so symmetrical in their construction that it makes little if any difference if the source and
drain terminals are swapped.
There are two channel types of JFETs. One type is n-channel and the other type is p-
channel. Both types operate exactly the same way but the terminal voltages and currents
are inverted. This discussion is for n-channel devices.
1
2. JFET Basics
The main feature of JFETs is extremely high input resistance – usually at least several
hundred megohms. This feature enables the power gain of a JFET amplifier to be huge.
Development of analytic equations for JFET bias condition
The following discussion is about n-channel JFETs. p-channel JFETs operate the same
way except that the polarity of the terminal voltages and currents is inverted. There are
two parameters that describe the operation of a JFET:
IDSS is the drain saturation current at VGS = 0.
VP is the gate-source voltage, VGS, that causes the channel conduction to drop to zero
(actually, the drain current does not go all the way to zero but ceases to decrease
below a very small current).
IDSS and VP have a rough proportional relationship. A high IDSS generally has a higher
magnitude VP. However, because the relationship is dependent on the manufacturing
geometry of the JFET there is not a singular proportionality constant. The interpretation
of this is that for the spread of IDSS and VP provided on the data sheet for a specific part
that low values of one parameter tend to correlate with low values of the other parameter
with the same holding true for higher values. Some data sheets show a typical plot of this
relationship.
The drain current is zero when VGS = VP and is IDSS when VGS = 0. The relationship in
the saturation region follows a square law as shown in Equation 1. For normal operation,
VGS is biased to be somewhere between VP and 0. Equation 1 gives the approximate
drain current, ID, for a given bias point. This approximation is generally good to within
about ten percent and is the accepted equation for all JFET calculations. The more exact
model is discussed later.
2
ID = IDSS * [1 - (VGS/VP)] Eq. 1
Equation 1 is valid only if the JFET is operating such that VGS is between 0 and VP and
that VDS is greater than (VGS - VP) , i.e. the saturation region. Note that the drain current,
ID, will be between 0 and IDSS. Figure 2 illustrates an example transfer function for a
JFET that has an IDSS of 12 mA and a VP of -6 volts. The drain current will be less if the
transistor is operating in the ohmic region. Although the transfer curve continues into the
positive bias region we do not normally operate the JFET there except for very small
signals.
2
3. JFET Basics
Transfer Curve of a Typical JFET
0.015
0.014
0.013
0.012
0.011
0.010
0.009
0.008
ID
0.007
0.006
0.005
0.004
0.003
0.002
0.001
0.000
-7.0 -6.0 -5.0 -4.0 -3.0 -2.0 -1.0 0.0
VGS
Figure 2: Transfer Curve of a Typical JFET showing ID versus VGS
Figure 3 shows the family curves for a typical JFET. For amplifiers we normally operate
the JFET in the saturation region to the right of the dotted parabola curve that separates
the ohmic region from the saturation region. Note that that the dotted curve is the
solution to VDS = (VGS – VP). In the ohmic region the device acts similarly to a voltage
controlled resistor and in the saturation region the device acts as a voltage controlled
current source. The slight tilt of the lines in the saturation region is an extension of the
model that includes the effective shunt resistance of the current source. That model is not
discussed here. All of the mathematics developed later assumes these lines are perfectly
horizontal. It should be noted that for VDS near zero volts (within plus or minus a few
tenths of a volt at most) the channel acts as a voltage variable resistor that is linear with
voltage. This useful effect continues through zero for small negative voltages across the
channel.
3
4. FET Family Curves
for IDSS = 12 mA and VP = -6
0.015
0.014
Ohmic_region Saturation_region
0.013
VGS=0
0.012
0.011 VGS=-1
0.010
VGS=-2
0.009
0.008
ID
VGS=-3
0.007
0.006
VGS=-4
0.005
0.004
VGS=-5
0.003
0.002 VGS=-5.5
0.001
0.000 Knee
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
VDS
Figure 3: FET Family Curves
Note: VGS is negative – the minus sign may not show on some systems
It is desirable to have the solution to every possible permutation of knowns. The next
task is to solve Equation 1 for VGS if ID is known. This is an exercise for the student but
the result is:
VGS = VP * [1 - sqrt(ID/IDSS)] Eq. 2
Equations 1 and 2 tell us about the DC bias point operation of the JFET for any
combination of knowns.
Development of gain equations for the JFET
Since the JFET is a voltage controlled current source, the gain is the change in drain
current divided by the change in gate voltage. This is called the transconductance gain
(abbreviated as gm) of the JFET and has units of conductance which is measured in
Siemens. The gain value is very low (typically between 0.0001 and 0.02 – but remember
that what matters is power gain and that is very high for a JFET) and is often expressed in
mS. The gain is found by taking the derivative of Equation 1 with respect to VGS.
gm = |2 * (IDSS/VP) * [1 - (VGS/VP)]| Eq. 3
5. The absolute value is used because gm is always positive. This is done because sign
information is lost when terms are squared as in Equation 1. The ratio, IDSS/VP, will
always be negative since VP is negative for n-channel JFETS and IDSS is negative for
p- channel JFETS.
Note from Equation 3 that gm is a linear function of VGS. When VGS is equal to VP (i.e. ID
is zero) then gm is zero. When VGS is equal to zero (i.e. ID = IDSS) then gm is at the
maximum value. The maximum value of gm is known as gmo and is obtained by setting
VGS to zero in Equation 3.
gmo = |2 * (IDSS/VP)| Eq. 4
At this point it should seem obvious that if high gain is desired then the JFET should be
biased as close as practical to IDSS. Equation 4 gives us the ultimate gain possible.
Equation 3 gives us the gm if VGS is known. For some problems, ID is known instead.
Although VGS can be calculated if ID is known, it is convenient to have an equation that
directly gives us gm when ID is known. Simple substitution of Equation 1 into Equation 3
(an exercise for the student) gives:
gm = |2 * sqrt(ID * IDSS) / VP| Eq. 5
Equation 5 can be expressed in another way that might be convenient for some problems
gm = gmo * sqrt(ID/IDSS) Eq. 6
All three ways of computing gm give exactly the same answer. The one to use depends on
what the knowns at the moment are. It must be remembered that all of these equations
assume the JFET is operating in the saturation region. They do not apply in the ohmic
region. The user must always take care in using these equations.
The scale factor of 2 in Equations 3 through 5 is nominal. According to the National
Semiconductor FET Handbook (1977), that factor can range from about 1.1 to 2.5 but is
typically near 2. Keep in mind that we use a model of a JFET based on a simplified
quadratic equation.
Equations 1 and 2 can be expressed in a normalized form as
2
ID/IDSS = [1 – (VGS/VP)] Eq. 7
VGS/VP = 1 – sqrt(ID/IDSS) Eq. 8
6. An equation for the normalized gm can be developed by dividing Equation 3 by Equation
4 producing
gm/gmo = 1 – VGS/VP Eq. 9
By substituting Equation 8 into Equation 9 we can also write
gm/gmo = sqrt(ID/IDSS) Eq. 10
Figure 4 is a plot of Equations 7 and 9. The linear relationship between VGS and gm is
clearly seen. Figure 5 is a plot of Equation 10.
Normalized ID/IDSS and gm/gmo versus VGS/VP
1.000
0.900
0.800
0.700
0.600
ID/IDSS
ID/IDSS
0.500
gm/gmo
0.400
0.300
0.200
0.100
0.000
0.00 0.10 0.20 0.30 0.40 0.50 0.60 0.70 0.80 0.90 1.00
VGS/VP
Figure 4: Normalized FET plot
7. gm/gmo versus ID/IDSS
1.000
0.900
0.800
0.700
0.600
gm/gmo
0.500
0.400
0.300
0.200
0.100
0.000
0.000 0.100 0.200 0.300 0.400 0.500 0.600 0.700 0.800 0.900 1.000
ID/IDSS
Figure 5: Normalized gm/gmo
Comparing “Exact” and Approximate JFET Models
In the text, Engineering Electronics, A Practical Approach, by Robert Mauro (copyright
1989 by Prentice-Hall, Inc., Englewood Cliffs, NJ 07632) on pages 209 to 211 there is a
development of a more accurate mathematical model for the JFET. The result of that
development is:
3/2
[ (VGS) (VGS) ]
ID = IDSS * [ 1 – 3 * (-----) + 2 * (-----) ] Eq. 11
[ ( VP ) ( VP ) ]
A commonly used and more convenient approximate model was presented in Equation 1
and is expanded here for comparison:
2
[ (VGS) (VGS) ]
ID = IDSS * [ 1 – 2 * (-----) + (-----) ] Eq. 12
[ ( VP ) ( VP ) ]
8. Figure 6 is a plot of both equations in normalized form. Observe that the error of the
approximate model is not very large and that the approximate model predicts a somewhat
higher current than the actual. Observe also that the slope of the “exact” curve is steeper
thus leading to a higher gm.
Comparing "Exact" versus Approximate JFET Models
1.00
0.90
0.80
0.70
0.60
Normalized ID
ID approx
0.50 ID exact
ID error
0.40
0.30
0.20
0.10
0.00
0.00 0.10 0.20 0.30 0.40 0.50 0.60 0.70 0.80 0.90 1.00
VGS/VP
Figure 6: Comparing “Exact” versus Approximate JFET Models
Figure 7 shows the normalized transconductance for both models. Observe that the
“exact” model has a higher gmo than the approximate model. This is one reason that on
data sheets the stated value of gmo is often higher than what one would calculate using the
given IDSS and VP parameters.