FETs

11 Key excerpts on "FETs"

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  eBook - PDF

  Introduction to Analogue Electronics

  • B. Hart(Author)
  • 1996(Publication Date)
  • Butterworth-Heinemann

    (Publisher)

  5 Field effect transistors (FETs): d.c.-characterization and biasing The FET is the second type of semiconductor control device that has helped to catapult the subject of electronics from a subsidiary to a central role in engineering and scientific disciplines. It operates on an entirely different principle from that of the BJT, leading to some associated circuit properties, e.g. very high input impedance, than can be exploited by the equipment design engineer. In a BJT the flow of minority carriers, across a base region from emitter to collector is dependent upon potential differences (V BE, V CB) that act in the direction of carrier flow. The FET, by contrast, is a semiconductor device in which the flow of majority carriers in a 'channel' between two terminals designated source (8) and drain (D) is dependent upon a transverse field resulting from the application of a potential difference between one of these terminals (normally, S) and a third, control, terminal known as the gate (G). A crude everyday analogy is a garden hose pipe, in which the flow of water can be controlled by a squeezing action in a direction perpendicular to the direction of flow. The particular way in which the electrical control function is achieved, without the requirement of significant d.c. input power, permits a division of FETs into two basic categories each of which can be further sub-divided. This chapter considers the classification of FETs, discusses the characteristics of one popular type in some detail and shows how it can be biased for use in d.c. and in low-frequency small-signal amplifier applications. 5.1 THE FET FAMILY The junction gate FET (Jugfet, JFET) On each side of a PN junction there is a narrow layer devoid of charge carriers The P-side layer has a net negative charge resulting from fixed negatively-charged acceptor impurity atoms that have supplied holes which are elsewhere in the crystal lattice.

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  Basic Electronics

  Principles and Applications

  • Chinmoy Saha, Arindam Halder, Debarati Ganguly(Authors)
  • 2018(Publication Date)
  • Cambridge University Press

    (Publisher)

  Chapter 7 Field-Effect Transistors 7.1 INTRODUCTION The field-effect transistor, customarily known as FET, like bipolar junction transistor (BJT), is a three-terminal semiconductor device extensively used in numerous electronic circuits and systems ranging from digital logic circuits to amplifier design. The term ‘ field effect ’ arises due to the fact that applied external electric field creates a conduction path called channel and controls the output current of the device. Even though FET has various structural and operational similarities with BJT, they have some fundamental differences, which are as follows:  In BJT, the current is contributed by two types of carriers: electrons and holes (hence the term ‘ bi ’, meaning two, which justifies its name bipolar ). In case of FET, based on its structure, only one type of carrier, i.e. either electron or hole, contributes to the current. Hence, it is known as a unipolar device. Due to this, FETs do not suffer from minority carrier storage effects and consequently have higher switching speeds and higher cut-off frequencies.  BJT is a current-control device, where output current I C is solely controlled by the input current I B with a relation I C ≈ βI B . On the other hand, FET is a voltage-controlled device, where the voltage between two terminals V GS controls the output current I D . This is indicated in the schematic block diagram of Figure 7.1. Thus, FET is termed as a voltage-controlled device. 408 Basic Electronics One of the most important features of FET is its very high input impedance, typically much higher than that of BJT. This makes FETs a very good choice for designing linear amplifiers. Another advantageous feature of FETs is their better temperature stability compared to BJT. At high current level, FET offers negative temperature coefficient of current (meaning that current decreases due to increase in temperature). Due to this phenomenon, FETs can prevent thermal runaway.

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  eBook - ePub

  Electronic Devices and Circuit Fundamentals

  • Dale R. Patrick, Stephen W. Fardo, Ray E. Richardson, Vigyan (Vigs) Chandra(Authors)
  • 2023(Publication Date)
  • River Publishers

    (Publisher)

  metal-oxide semiconductor field-effect transistor (MOSFET). Both classifications of the FET play an important role in solid-state electronics and are studied in this chapter.

  Objectives

  After studying this chapter, you will be able to:

  • 8.1 analyze the operation of a junction field-effect transistor;
  • 8.2 analyze the operation of E-MOSFET, D-MOSFET, and V-MOSFET transistors;
  • 8.3 analyze and troubleshoot field-effect transistors.

  Chapter Outline

  • 8.1 Junction Field-Effect Transistors
  • 8.2 Metal-Oxide Semiconductor FETs
  • 8.3 Analysis and Troubleshooting – Field-Effect Transistors

  Key Terms

  channel depletion metal-oxide semiconductor field-effect transistor (D-MOSFET) drain dynamic transfer curve enhancement metal-oxide semiconductor field-effect transistor (E-MOSFET) gate junction field-effect transistor (JFET) ohmic region pinch-off region source substrate transconductance vertical metal-oxide semiconductor field-effect transistor (V-MOSFET)

  8.1 Junction Field-Effect Transistors

  The junction field-effect transistor (JFET) is a three-element electronic device. Its operation is based on the conduction of current carriers passing through a single piece of semiconductor material instead of a junction. The two major types of JFETs are N-channel and P-channel. JFET circuit operation can be predicted with a family of characteristic curves chart and a dynamic transfer curve. In this section, you will learn about the characteristics and operation of N-channel and P-channel JFETs. You will use a family of characteristic curves and a dynamic transfer curve to predict the operation of a JFET and will learn how to read and interpret a JFET data specifications sheet.

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  Introductory Quantum Mechanics for Applied Nanotechnology

  • Dae Mann Kim(Author)
  • 2016(Publication Date)
  • Wiley-VCH

    (Publisher)

  Chapter 19 Field-Effect Transistors

  The idea of field-effect transistors (FETs) was conceived as early as 1930s and successfully implemented in 1960s. The advantages of FET as exemplified by MOSFET consist of the simplicity of structure, low-cost processing, and scalability for use in multifunctional integrated circuits. The well-known theory of MOSFET is first discussed as the general background for modeling the I–V behavior in other kinds of FETs, for example, silicon nanowire (NW), ballistic, and tunneling FETs. An emphasis is placed on highlighting the underlying quantum mechanical concepts.

  19.1 The Modeling of MOSFET I–V

  MOSFET is a three-terminal, normally off, and unipolar device, and its central role consists of electrical switching for the digital logic functions. The device is also extensively utilized as the platform for memory, sensor, and green energy applications and has been downscaled deep into the nanoregime.

  I–V Characteristics

  Thus, consider NMOS consisting of the n+ source and drain on p-type substrate and the n+ polysilicon gate electrode, which is insulated from the substrate via SiO2 (Figure 19.1 ). The source and drain electrodes form with the p substrate n+ –p and p–n+ junctions back to back. Hence, with the gate voltage off ( ) and the drain voltage on ( ), the p–n+ junction at the drain end is reverse biased, cutting off the current (off state). But with V

  G

  on greater than the threshold voltage VT , the junction barrier at the source end is lowered, and electrons are injected from the source into the channel and contribute to the drain current ID . Also shown in the figure are the transistor and transfer ID –VG curves. Each transistor curve consists of triode and saturation regions. In the former, I

  D

  increases linearly or sublinearly with V

  D

  and saturates at a nearly constant level in the latter. The ON to OFF current ratio typically of 106

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  Fundamentals of Electronics

  Book 1 Electronic Devices and Circuit Applications

  • Thomas F. Schubert, Ernest M. Kim(Authors)
  • 2022(Publication Date)
  • Springer

    (Publisher)

  229 C H A P T E R 4 Field Effect Transistor Characteristics In Chapter 3 Bipolar Junction Transistors were shown to be semiconductor devices that operate on carrier flow from the emitter to the base and then through to the collector. For example, npn BJTs are devices where the current flow from the collector to the emitter is regulated by the current injected into the base. erefore, the BJT is a current controlled three-terminal semiconductor device. Field Effect Transistors (FETs) are semiconductor devices that employ a channel between the drain and the source to transport carriers. An adjacent controlling surface, called the gate, regulates the current flow through the drain-source channel. is channel is controlled by a volt- age applied to the gate of the FET. erefore, the FET can be described as a voltage controlled three-terminal semiconductor device (see Figure 4.1). e physical properties of FETs make them suitable for amplification, switching, and other electronic applications. '&5 %SBJO % (BUF ( 4PVSDF 4 $VSSFOU I Figure 4.1: FET represented as a three terminal device. e terminal characteristics of Junction Field Effect Transistors ( JFETs) and Metal-Oxide- Semiconductor FETs (MOSFETs) are described in this chapter. Other types of FETs exist, but JFETs and MOSFET are the predominate FET types.¹ MOSFETs are used extensively in inte- grated circuits for digital applications: JFETs are most commonly found in analog applications. ¹Other FET types include the Metal-Semiconductor FET (MESFET), Modulation-doped FET (MODFET), and Vertical MOSFET (VMOSFET). Analysis of JFETs and MOSFETs will allow for a general understanding of FET behavior that can be used with other FET devices. 230 4. FIELD EFFECT TRANSISTOR CHARACTERISTICS Terminal characterization of FETs is sufficient for electronic analysis and design: for discussions on the device physics of FETs, the reader is referred to the references.

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  eBook - ePub

  Intuitive Analog Circuit Design

  • Marc Thompson(Author)
  • 2013(Publication Date)
  • Newnes

    (Publisher)

  Chapter 9

  Introduction to Field-Effect Transistors (FETs) and Amplifiers

  Abstract

  We next take a detour from the world of bipolar transistors and enter the world of field-effect transistors. The basic signal metal oxide–semiconductor (MOS) structure is discussed, followed by a discussion of metal oxide–semiconductor field-effect transistor amplifiers. The incremental model of the MOS transistor is shown, and it is used in a design example where gain and bandwidth are calculated for an MOS amplifier. We then finish with the junction field-effect transistor (JFET) and several examples of JFET amplifiers.

  Keywords

  Field-effect; JFET; MOSFET; drain current; saturation; Ohmic region; source; follower; common-source amplifier; common-gate amplifier; MOS current mirror; design example; shunt peaked amplifier

  “Our life is frittered away by detail. Simplify, simplify, simplify!” —Henry D. Thoreau

  IN THIS CHAPTER

   We next take a detour from the world of bipolar transistors and enter the world of field-effect transistors (FETs). The basic signal metal oxide–semiconductor (MOS) structure is discussed, followed by a discussion of metal oxide–semiconductor field-effect transistor (MOSFET) amplifiers. The incremental model of the MOS transistor is shown, and it is used in a design example where gain and bandwidth are calculated for an MOS amplifier. We then finish with the junction field-effect transistor (JFET) and several examples of JFET amplifiers.

  Early history of field-effect transistors

  The invention of the MOSFET predates the bipolar transistor. An excerpt from one US patent granted in 1933 to Dr Julius Lilienfeld is shown in Figure 9.1

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  Silicon, From Sand to Chips, Volume 1

  Microelectronic Components

  • Alain Vignes(Author)
  • 2024(Publication Date)
  • Wiley-ISTE

    (Publisher)

  6 The MOSFET Transistor Research on the effect of an electric field on the conductivity of a doped semiconductor wafer, by William Shockley as early as 1945, led to the demonstration of a direct field effect as early as 1947 by John Bardeen and Walter (see Chapter 3, section 3.1.2.2). But due to the problem of “surface states” (traps), it was not until 1959 that the first silicon MOSFET was produced by Martin Atalla and Dawon Kahng of Bell Labs. It was the qualities of silicon oxide that led to the development of the silicon-based MOSFET transistors. The first commercial transistors appeared in 1964. The MOSFET transistor became the preferred component for computer logic circuits and memories in 1970, because of its low power consumption and miniaturization capacity. Miniaturization by a factor of 1,000 has been achieved in 50 years, which means a reduction in the switching time by a factor of 1,000 and therefore an increase in operation speed. The miniaturization of transistors has posed acute problems in terms of manufacturing processes, dielectric and electrode materials for the gate, source and drain, and electrical connections. This chapter presents: – the transistor operation (in static regime); 176 Silicon, From Sand to Chips 1 – the functions: switching and amplification; – the CMOS component; – the development history of the MOSFET transistor; – the evolution of MOSFET transistor materials imposed by miniaturization (Moore’s law). 6.1. Features and functions 6.1.1. Introduction The field effect (presented in Chapter 3, section 3.1.1) consists of the polarization (conductivity inversion and/or modulation) of a thin surface layer of a wafer or thin film of a doped semiconductor, induced by the application of an electrostatic field perpendicular to the semiconductor surface via a flat electrode close to and parallel to the wafer surface.

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  Frontiers of Thin Film Technology

  • Stephen M. Rossnagel, Abraham Ulman(Authors)
  • 2000(Publication Date)
  • Academic Press

    (Publisher)

  THIN FILMS, VOL. 28 Field Effect Transistors: FETs AND HEMTs PRASHANT CHAVARKAR AND UMESH MISHRA Department of Electrical and Computer Engineering, University of California, Santa Barbara, California, USA Abstract This chapter discusses the principles of operation and applications of field effect transistors. Field effect transistors, specifically high electron mobility transistors (HEMTs) or modulation-doped field-effect transistors are being extensively used in low noise and power amplifiers at microwave and millimeter-wave frequencies. The chapter begins with a discussion of current voltage and charge control mechanisms in HEMTs and this is followed by discussion of small-signal and large-signal equivalent circuit models of FET (which are used in circuit design). As operation at high frequencies is enabled by reduction in gate length, issues relating to device scaling are discussed. Issues related to operation of FETs as low-noise and power amplifier devices are discussed. The emergence of crystal growth techniques including molecular beam epitaxy (MBE) and metalorganic chemical vapor deposition (MOCVD) has enabled the fabrication of HEMTs using a variety of material systems. The selection of a material system depends on application and operating frequency. The A1GaAs/InGaAs pseudomorphic HEMT and the AlInAs/GaInAs HEMT are the two most widely used device structures. The performance of these devices as low-noise and power amplifica- tion devices is summarized. These devices have recently demonstrated their ability for insertion in high-volume commercial applications such as wireless and optical communication systems. This chapter therefore discusses the various design issues involving power amplifiers for wireless handsets and the suitability of GaAs pHEMTs for this application. The AlInAs/GaInAs HEMT with its high current density and superior high frequency performance has enabled the fabrication of digital circuits operating at 80 Gb/s.

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  A Guide to Noise in Microwave Circuits

  Devices, Circuits and Measurement

  • Peter Heymann, Matthias Rudolph(Authors)
  • 2021(Publication Date)
  • Wiley-IEEE Press

    (Publisher)

  Depending on the gate voltage, the depletion layer expands into the channel and thus controls the drain current. The MESFET is a barrier The Pucel Model 215 field effect transistor with a Schottky contact as gate electrode. The material is usually Gallium Arsenide (GaAs), for special applications also Gallium Nitride (GaN) or Indium Phosphide (InP). While the characteristic properties and the mode of operation are very similar to the JFET, there are some special features in the noise properties. The dimensions of the device chips are very small and the typical channel lengths are a few micrometers. The gate lengths L < 0.5 μ m. There-fore very high field strengths occur in the channel in longitudinal direction. The simple approach to the thermal behavior of the channel with constant mobility 𝜇 , as we did for the JFET (11.3), is no longer applicable here. The electrons move in the range of the saturation drift velocity, or in the range of the negative differential mobility (above 5 kV/cm) in the case of GaAs. Thus they are no longer in thermal equilibrium with the bulk material, and they have an increased electron temper-ature. However, the term electron temperature is not correct, because it implies a Maxwellian velocity distribution, which is also not present here. In addition, the small spatial dimensions are in the range of the free path, so that physical con-cepts like mobility and temperature are not applicable. The contribution of these hot electrons to the noise of the channel is summarized under the general term high-field diffusion noise. Its quantitative description is the subject of complicated theories. In practice, fitting parameters are widely used. In the microwave range, in addition to this overthermal noise, the thermal noise of the parasitic resistors also plays an increasing role.

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  Field-Effect and Bipolar Power Transistor Physics

  • Adolph Blicher(Author)
  • 2012(Publication Date)
  • Academic Press

    (Publisher)

  The overlap capacitances can be minimized by using self-aligned polycrystalline gates, for example. Generally, the drain-to-gate capacitances are efficiently minimized in power devices with such structures as the off-set gate devices and vertical drain transistors, where the drain electrode is well decoupled from the gate. The use of thicker oxide under the gate metal in areas other than those directly over the active channel regions is also helpful in reducing the parasitic capacitances. Transistors with -channels as amplifiers are superior in many respects to the p-channel devices because of the higher electron mobility, better frequency response, and higher transconductance. Materials other than silicon have been used to improve the MOST transconductance and increase its operating temperature beyond the ~ 175 C limit of silicon devices. The most prominent of these materials is the III-V compound GaAs. Its high electron mobility and wide energy gap make it particularly attractive for this purpose. Not much progress has been made in this area after the first successful results obtained by [1] with the GaAs -channel depletion-type transistor. The difficulty rests here primarily with the presence of the very high density of the interface states between GaAs and the gate insulator. MESFETs, described in Chapter 11, do not have this problem since their gate depletion region extends well below the GaAs surface. 13.2 MOS Power Transistor as a Switch MOS power transistors are capable of switching large currents with voltage drops comparable to but still somewhat higher than those of bipolar transistors with silicon dies of the same active area. The voltage drop re sulting from the presence of the on-state resistance R on is one of the most important parameters of a switch, as it determines the amount of dissipated energy due to Joule heating. Figure 2 shows the idealized switching waveforms of the input gate-to-source voltage V G and the output current I D .

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  Solid State Chemical Sensors

  • Jiri Janata(Author)
  • 2012(Publication Date)
  • Academic Press

    (Publisher)

  S O L I D S T A T E C H E M I C A L S E N S O R S 2 Chemically Sensitive Field Effect Transistors JIRÎ JANATA D E P A R T M E N T O F B I O E N G I N E E R I N G T H E U N I V E R S I T Y O F U T A H S A L T L A K E C I T Y , U T A H I. General Theory 66 A. Historical Perspective 66 B. Qualitative Comparison of ISE, CWE, and ISFET 66 II. Thermodynamics of ISFETs 71 A. Neutral Species 76 B. CHEMFETs with Nonpolarized Interfaces—ISFETs 77 C. CHEMFETs with Polarized Interfaces 80 D. CHEMFETs with Nonconventional Membranes 88 E. Temperature Dependence of the ISFET 92 III. Dynamic Characteristics 93 A. Transients due to Change of Gate Voltage 93 B. Transients due to Change of Drain Current 95 C. Equilibrium Noise in ISFETs 97 IV. Measuring Systems 101 A. Reference Electrodes 101 B. Measuring Circuits 103 V. Special CHEMFETs 108 A. Enzymatically Sensitive Field Effect Transistor (ENFET) 108 B. Electrostatically Protected ISFET 111 C. Micro ISFET 113 D. CHEMFET with Universally Accessible Gate 114 VI. Conclusions 115 References 116 Copyright © 1985 by Academic Press, Inc. All rights of reproduction in any form reserved. ISBN 0-12-380210-5 65 66 Jlfti JANATA I. General Theory A. HISTORICAL PERSPECTIVE Developments in electronics and computer technologies over the past 40 years have had a major impact on analytical chemistry: operation amplifiers revolutionized almost every area of instrumental analysis in the 1950s and 1960s and, more recently, microprocessors have improved the precision and convenience of use of existing analytical techniques far beyond previous limits. Lasers and dedicated digital circuits have led to completely new methods of instrumental analysis. The role that electron-ics plays can be clearly traced in the history of the old electroanalytical technique—potentiometry. The fundamental concept of potentiometry is simple: one measures the difference of inner potentials of the metal of the indicator electrode and a well-defined reference electrode.

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