Physics
FET Configuration
The FET (Field Effect Transistor) configuration refers to the arrangement of components in a FET circuit. It determines the behavior and performance of the FET, such as amplification or switching characteristics. Common FET configurations include common source, common gate, and common drain, each with its own advantages and applications in electronic circuits.
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eBook - PDFElectronic Concepts
An Introduction
- Jerrold H. Krenz(Author)
- 2000(Publication Date)
- Cambridge University Press(Publisher)
An understanding of the physical operation of a MOSFET device is neces-sary to devise suitable equivalent circuit models. These models will then be used to develop an understanding of several commonly used MOSFET circuits. It is these circuits, when combined in very-large-scale integrated circuits, that have revolutionized the diversity and complexity of modern electronic systems. 4.1 FIELD-INDUCED CARRIERS: THE PHYSICS OF A MOSFET DEVICE Although a quantitative description of a MOSFET device premised on a detailed understanding of semiconductor physics is beyond the scope of an introduc-tory text, a qualitative description of the key physical mechanisms involved is desirable. The device of Figure 4.7, a device with a p-type substrate in which free electrons are the current carriers, will be considered. Because the carriers of the MOSFET device are free electrons that form a channel between the source and drain, an ra-channel designation is used. To simplify the analysis, a common 4.1 FIELD-INDUCED CARRIERS: THE PHYSICS OF A MOSFET DEVICE 221 Si 3 t ox = oxide thickness, m e ox = permitivity of oxide, F/m IJL n = surface mobility of free electrons, m 2 /V-s C ox = gate capacitance, eox/tox, F/m 2 Vj = threshold voltage, V Figure 4.7: Metal-oxide field-effect transistor configuration. connection for the source and substrate will be assumed; the effect of a source-to-substrate bias will be treated later. Complementary devices with an «-type substrate in which holes are the current carriers, that is, a p-channel MOSFET device, are also widely used. It is the gate-to-substrate capacitance, the result of the thin silicon dioxide dielectric that separates the gate and substrate, that plays a pivotal role in the behavior of the device. For a zero gate-to-substrate bias (Figure 4.8(a)), the sub-strate, except in the vicinity of the w-type regions, tends to have a uniform dis-tribution of holes, and the hole density is approximately equal to the acceptor doping density.
eBook - PDF- 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.
eBook - ePub- 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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