JFET .

• JFET

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Electronic engineering - Electronic devices and circuits

1 Electronic devices: Energy bands in silicon, intrinsic and extrinsic silicon. Carrier transport in silicon: diffusion current, drift current, mobility,

resistivity. Generation and recombination of carriers. p-n junction diode, Zener diode, tunnel diode, BJT, JFET, MOS capacitor, MOSFET, LED,

p-i-n and avalanche photo diode, LASERs. Device technology: integrated circuit fabrication process, oxidation, diffusion, ion implantation,

photolithography, n-tub, p-tub and twin-tub CMOS process.


Electronic engineering - Electronic devices and circuits

1 Analog circuits: Equivalent circuits (large and small-signal) of diodes, BJTs, JFETs, and

MOSFETs


MOSFET - Circuit symbols

1 Comparison of enhancement-mode and depletion-mode MOSFET

symbols, along with JFET symbols (drawn with source and drain ordered

such that higher voltages appear higher on the page than lower

voltages):


Electronic component - Transistors

1 JFET (Junction Field-Effect Transistor) – N-

CHANNEL or P-CHANNEL


Electronic component - Optoelectronic devices

1 Opto-Isolator, Opto-Coupler, Photo-Coupler – Photodiode, BJT, JFET, SCR,

TRIAC, Zero-crossing TRIAC, Open collector IC, CMOS IC, Solid state

relay (SSR)


Semiconductor device - Transistor

1 The field may be applied by a reverse-biased p–n junction, forming

a junction field-effect transistor (JFET) or by an electrode isolated

from the bulk material by an oxide layer, forming a metal–oxide–

semiconductor field-effect transistor (MOSFET).


Transistor

1 Structure: BJT, JFET, IGFET (MOSFET), insulated-gate bipolar transistor, "other

types"


Transistor

1 Functionally, this makes the n-channel JFET the solid-state

equivalent of the vacuum tube triode which, similarly, forms a diode between its grid and cathode


Transistor

1 Metal–semiconductor FETs (MESFETs) are JFETs in which the reverse biased p–n

junction is replaced by a metal–semiconductor junction. These, and the

HEMTs (high-electron-mobility transistors, or HFETs), in which a two-dimensional

electron gas with very high carrier mobility is used for charge transport, are especially suitable for use at very high frequencies (microwave frequencies; several GHz).


Transistor

1 Unlike bipolar transistors, FETs do not inherently amplify a photocurrent.

Nevertheless, there are ways to use them, especially JFETs, as light-

sensitive devices, by exploiting the photocurrents in channel–gate or

channel–body junctions.


Transistor

1 Nearly all JFETs are depletion-mode because the diode junctions would forward bias and conduct if they

were enhancement-mode devices; most IGFETs are enhancement-mode

types.


Transistor

1 JFET, where the gate is insulated by a reverse-biased

p–n junction


Transistor

1 MESFET, similar to JFET with a Schottky junction instead of a

p–n junction


JFET

1 The junction gate field-effect transistor (JFET or JUGFET) is the simplest type of

field-effect transistor. It can be used as an electronically-controlled switch or as a voltage-controlled resistance. Electric

charge flows through a semiconducting channel between "source" and "drain" terminals. By applying a reverse bias

voltage to a "gate" terminal, the channel is "pinched", so that the electric current is

impeded or switched off completely.https://store.theartofservice.com/itil-2011-foundation-complete-certification-kit-fourth-edition-study-guide-ebook-and-online-course.html

JFET - Structure

1 The JFET is a long channel of semiconductor material, doped to contain an abundance of positive charge carriers or holes (p-type), or

of negative carriers or electrons (n-type). Ohmic contacts at each end form the

source (S) and drain (D). A pn-junction is formed on one or both sides of the channel,

or surrounding it, using a region with doping opposite to that of the channel, and

biased using an ohmic gate contact (G).


JFET - Function

1 JFET operation is like that of a garden hose. The flow of water through a hose

can be controlled by squeezing it to reduce the cross section; the flow of

electric charge through a JFET is controlled by constricting the current-carrying

channel. The current also depends on the electric field between source and drain (analogous to the difference in pressure

on either end of the hose).


JFET - Function

1 Some JFET devices are symmetrical

with respect to the source and drain.


JFET - Schematic symbols

1 The JFET gate is sometimes drawn in the middle of the channel (instead of at the drain or source electrode as in

these examples). This symmetry suggests that "drain" and "source" are interchangeable, so the symbol should be used only for those JFETs

where they are indeed interchangeable.


JFET - Comparison with other transistors

1 At room temperature, JFET gate current (the reverse leakage of the gate-to-channel

junction) is comparable to that of a MOSFET (which has insulating oxide between gate and channel), but much less than the base current of a bipolar junction transistor. The JFET has higher transconductance than the MOSFET, as well as lower flicker noise, and is therefore used in some low-noise, high

input-impedance op-amps.


JFET - History of the JFET

1 The first practical JFETs were made many years later, in spite of their

conception long before the junction transistor


JFET - Mathematical model

1 The current in N-JFET due to a small voltage

VDS is given by:


Diode - Types of semiconductor diode

1 These are actually JFETs with the gate shorted to the source, and

function like a two-terminal current-limiter analog to the Zener diode,

which is limiting voltage. They allow a current through them to rise to a

certain value, and then level off at a specific value. Also called CLDs, constant-current diodes, diode-

connected transistors, or current-regulating diodes.


Electronic symbol - Reference designations

1 JFET: Junction gate field-effect transistor


Electronic symbol - Transistors

1 n-channel junction gate field-effect transistor

(JFET)


Electronic symbol - Transistors

1 p-channel junction gate field-effect transistor (JFET)


Field-effect transistor - History,

1 The field-effect transistor was first patented by Julius Edgar Lilienfeld in 1926 and by

Oskar Heil in 1934, but practical semiconducting devices (the JFET) were

developed only much later after the transistor effect was observed and explained by the team of William Shockley at Bell Labs in

1947. The MOSFET, which largely superseded the JFET and had a more profound effect on electronic development, was invented by Dawon Kahng and Martin Atalla in 1960.


Field-effect transistor - Types of field-effect transistors

1 The JFET (junction field-effect transistor) uses a reverse biased p–n junction to separate the gate from

the body.


Field-effect transistor - Types of field-effect transistors

1 The MESFET (metal–semiconductor field-effect transistor) substitutes the

p–n junction of the JFET with a Schottky barrier; and is used in GaAs

and other III-V semiconductor materials.


Silicon carbide - Power electronic devices

1 In 2008, the first commercial JFETs rated at 1200 V were introduced to the market, followed in 2011 by the first commercial MOSFETs rated at

1200 V


MOSFET - Circuit symbols

1 Comparison of enhancement-mode and depletion-mode MOSFET symbols, along with JFET symbols (drawn with source and drain ordered such that higher voltages appear higher on the page than lower voltages):[http://www.circuitstoday.com/electronic-

circuit-symbols Electronic Circuit Symbols]IEEE 315[http://highered.mcgraw-hill.com/sites/dl/free/0073191639/366537/Chapter_4.pdf#page=19 Microelectronic Circuit Design], Jaeger, Blalock - Figure


Schottky barrier - Devices

1 A MESFET, or metal–semiconductor field effect transistor|FET uses a reverse biased

Schottky barrier to provide a depletion region that pinches off a conducting channel buried inside the semiconductor (similar to

the JFET where instead a p–n junction provides the depletion region). A variant of

this device is the high-electron-mobility transistor (HEMT), which also utilizes a heterojunction to provide a device with

extremely high conductance.https://store.theartofservice.com/itil-2011-foundation-complete-certification-kit-fourth-edition-study-guide-ebook-and-online-course.html

Triode - Operation

1 The triode is very similar in operation to the n-channel JFET; it is normally

on, and progressively switched off as the grid/gate is pulled increasingly

negative of the source/cathode.


Threshold voltage

1 The threshold voltage of a JFET|junction field-effect transistor is often called 'pinch-off

voltage' instead, which is somewhat confusing since pinch off for an MOSFET|insulated-gate field-effect transistor is used to refer to the

channel length modulation|channel pinching that leads to current saturation behaviour

under high source–drain bias, even though the current is never off. The term threshold

voltage is unambiguous and refers to the same concept in any field-effect transistor.


Vacuum tube - Description

1 The solid-state device which operates most like the pentode tube is the junction field-effect transistor

(JFET), although vacuum tubes typically operate at over a hundred volts, unlike most semiconductors in

most applications.


Electronic component - Transistors

1 **JFET (Junction Field-Effect Transistor) – N-

CHANNEL or P-CHANNEL


Electronic component - Optoelectronic devices

1 ** Opto-isolator|Opto-Isolator, Opto-Coupler, Photo-Coupler – Photodiode, BJT, JFET, SCR, TRIAC, Zero-crossing TRIAC, Open collector IC, CMOS IC,

Solid state relay (SSR)


Constant current diode

1 'Constant-current diode' (also called 'CLD', 'current-limiting diode', 'diode-connected transistor' or 'CRD', 'current-regulating diode') consists of

a JFET with the gate shorted to the source, and it functions like a two-terminal current limiter or current source (analogous to a voltage-

limiting Zener diode)


SPICE - Device models

1 SPICE2 included many semiconductor device transistor models|compact models: three levels

of MOSFET model, a combined Ebers-Moll model|Ebers–Moll and Gummel–Poon model|

Gummel-Poon bipolar model, a JFET model, and a model for a diode|junction diode. In addition, it had many other elements: resistors, capacitors,

inductors (including Inductance#Coupled inductors|coupling), independent voltage source|voltage and current sources, ideal

transmission lines, and voltage and current controlled sources.


Education and training of electrical and electronics engineers - Electronic devices and circuits

1 'Electronic Devices': Energy bands in silicon, intrinsic and extrinsic silicon. Carrier transport in silicon: diffusion current, drift current, mobility,

resistivity. Generation and recombination of carriers. p-n junction diode, Zener diode, tunnel diode, BJT, JFET, MOS capacitor, MOSFET, LED,

p-I-n and avalanche photo diode, LASERs. Device technology: integrated circuits

fabrication process, oxidation, diffusion, ion implantation, photolithography, n-tub, p-tub and

twin-tub CMOS process.


Education and training of electrical and electronics engineers - Electronic devices and circuits

1 'Analog Circuits': Equivalent circuits (large and small-signal) of diodes, BJTs, JFETs, and

MOSFETs


Electronics engineering - Electronic devices and circuits

1 p-n junction diode, Zener diode, tunnel diode, BJT, JFET, MOS

capacitor, MOSFET, LED, p-i-n diode|p-i-n and avalanche photo-diode|avalanche photo diode, LASERs


Regenerative circuit - Advantages and disadvantages

1 Intrinsically, there is little or no difference in the gain and stability

available from vacuum tubes, JFET's, MOSFET's or bipolar junction

transistors (BJT's).


Channel (transistors) - Types of field-effect transistors

1 * The 'JFET' (junction field-effect transistor) uses a reverse biased p–n junction to separate the gate from

the body.


Channel (transistors) - Types of field-effect transistors

1 * The 'MESFET' (metal–semiconductor field-effect transistor)

substitutes the p–n junction of the JFET with a Schottky barrier; and is

used in GaAs and other III-V semiconductor materials.


Quite Universal Circuit Simulator - Components

1 There is also a Component library that includes various standard

components available in the market (bridges, diodes, varistors, LEDs,

JFETs, MOSFETS, and so on).


Overclocking - Cooling

1 Moreover, silicon-based junction gate field-effect transistors (JFET) will degrade below temperatures of roughly and eventually cease to

function or freeze out at since the silicon ceases to be semiconducting

so using extremely cold coolants may cause devices to fail.


Hartley oscillator - Operation

1 The most simple of implementations shown here uses nothing but a Junction FET|JFET (in

Common-drain configuration) and the LC tank circuit (here the single winding is

tapped), plus a single battery; it will work, but probably with high distortion and high current drain (that could be improved by

adding resistance between the source and the coil tap), and serves as an

uncomplicated illustration of the Hartley oscillator operation:


Hartley oscillator - Operation

1 * the output from the JFET's source (emitter, if a Bipolar Junction Transistor|BJT had been used;

cathode for a triode) has the same phase as the signal at its gate (or

base) - and roughly the same voltage as its input (which is the

voltage across the entire tank circuit), but the current is amplified,

i.e. it is acting as a Buffer amplifier#Current buffer|current buffer or VCVS|voltage-controlled

voltage-source.


P-type semiconductor - Use of extrinsic semiconductors

1 Field-effect transistors (FET) are another type of transistor

implementing extrinsic semiconductors. As opposed to BJTs,

they are unipolar and considered either N-channel or P-channel. FETs are broken into two families, JFET|

junction gate FET (JFET) and insulated gate FET (MOSFET|IGFET).


Metal oxide semiconductor field effect transistor - Circuit symbols

1 Comparison of enhancement-mode and depletion-mode MOSFET symbols, along with

JFET symbols


Gilbert cell - Function

1 A functionally equivalent circuit may be constructed using field-effect

transistors (JFET, MOSFET) or Thermionic valve|vacuum tubes.


Low-noise amplifier

1 For low noise, the amplifier needs to have a high amplification in its first stage. Therefore Junction Field-Effect Transistor|JFETs and High Electron Mobility Transistor|HEMTs are often

used. They are driven in a high-current regime, which is not energy-efficient, but reduces the relative amount of shot noise.

Input and output Impedance matching|matching circuits for narrow-band circuits

enhance the gain (see Gain-bandwidth product).


Ngspice - Status of Ngspice simulator

1 Ngspice implements various circuits elements, like resistors, capacitors,

inductors (single or mutual), transmission lines and a growing number of semiconductor devices

like diodes, bipolar transistors, mosfets (both bulk and SOI),

mesfets, jfet and HFET.


Transistors - Field-effect transistor (FET)

1 Metal–semiconductor FETs (MESFETs) are JFETs in which the Reverse-

biased|reverse biased p–n junction is replaced by a metal–semiconductor

junction. These, and the HEMTs (high-electron-mobility transistors, or

HFETs), in which a two-dimensional electron gas with very high carrier

mobility is used for charge transport, are especially suitable for use at very

high frequencies (microwave frequencies; several GHz).


Transistors - Field-effect transistor (FET)

1 Nearly all JFETs are depletion-mode because the diode junctions would forward bias and conduct if they

were enhancement-mode devices;


Transistors - Other transistor types

1 **JFET, where the gate is insulated by a reverse-

biased p–n junction


Transistors - Other transistor types

1 **MESFET, similar to JFET with a Schottky junction instead of a

p–n junction


List of computing and IT abbreviations - J

1 * JFET—Junction Field-Effect Transistor


AESA - Basic concept

1 The introduction of JFETs and MESFETs did the same to the transmitter side of the systems

as well


Current source - Current-stable nonlinear implementation

1 A JFET can be made to act as a current source by tying its gate to its source. The current then flowing is the IDSS of the FET. These can be purchased with this connection

already made and in this case the devices are called constant current diode|current regulator diodes or constant current diodes or current

limiting diodes (CLD).https://store.theartofservice.com/itil-2011-foundation-complete-certification-kit-fourth-edition-study-guide-ebook-and-online-course.html

Current source - Constant current diode

1 The simplest constant-current source or sink is formed from one

component: a JFET with its gate attached to its source. Once the drain-source voltage reaches a

certain minimum value, the JFET enters saturation where current is

approximately constant. This configuration is known as a constant-

current diode, as it behaves much like a dual to the constant voltage diode (Zener diode) used in simple

voltage sources.


Current source - Constant current diode

1 Due to the large variability in saturation current of JFETs, it is

common to also include a source resistor (shown in the image to the right) which allows the current to be

tuned down to a desired value.


MESFET

1 MESFETs are usually constructed in compound semiconductor

technologies lacking high quality surface passivation such as gallium arsenide|GaAs, indium phosphide|InP, or Silicon carbide|SiC, and are

faster but more expensive than silicon-based JFETs or MOSFETs


Nikon D2H

1 The 'Nikon D2H' is a professional-grade digital single-lens reflex camera introduced by Nikon Corporation on July 22, 2003. It uses Nikon's

own JFET-LBCAST sensor with a 4.1 megapixel resolution, and is optimised for sports and

action shooting that require a high frame rate. In 2005, the D2H was replaced by the D2Hs,

which added new features derived from the 12 megapixel Nikon D2X|D2X digital SLR. The D2Hs

was discontinued after the introduction of the Nikon D300|D300 and Nikon D3|D3 models.


Flicker noise

1 Flicker noise is often characterized by the corner frequency fc between the region dominated by the low-frequency flicker noise and the

higher frequency flat-band noise. MOSFETs have a higher fc (can be in the GHz range) than JFETs or bipolar transistors, which is usually below 2

kHz for the latter.


Power semiconductor device - Wide band-gap semiconductors

1 A SiC Schottky diode with a breakdown voltage of 1200V is

commercially available, as is a 1200V JFET


Tube sound - Tube sound from transistor amplifiers

1 In 1982, Tom Scholz, a graduate of MIT and a member of Boston (band)|

Boston, introduced the Rockman (music)|Rockman, which used

JFET/BJT-based operational amplifiers and diode-based clipping circuits, but achieved a distorted sound adopted

by many well known musicians. Advanced digital signal processing

offers the possibility to simulate tube sound. Algorithms are currently

available that transform digital sound from a CD or other digital source into

a distorted digital sound signal.


Trigate transistors - Flexfet

1 'Flexfet' is a planar, independently double-gated transistor with a

Copper interconnect|damascene metal top gate MOSFET and an

implanted JFET bottom gate that are self-aligned in a gate trench


Discrete transistor - Types

1 * Structure: Bipolar junction transistor|BJT, JFET, IGFET (MOSFET),

insulated-gate bipolar transistor, other types


Discrete transistor - Other transistor types

1 ** JFET, where the gate is insulated by a reverse-biased

p–n junction


Discrete transistor - Other transistor types

1 ** MESFET, similar to JFET with a Schottky junction instead of a p–n junction


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