Misplaced Pages

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82-425: Unlike bipolar junction transistors , JFETs are exclusively voltage -controlled in that they do not need a biasing current . 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. A JFET is usually conducting when there

164-441: A p -channel device requires p ositive V GS . In normal operation, the electric field developed by the gate blocks source–drain conduction to some extent. Some JFET devices are symmetrical with respect to the source and drain. 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

246-414: A GHT hose to a BSP fitting, or vice versa, will damage the threads. The connector threads are not tapered, and do not seal against leaks. Instead, a pliable rubber or plastic gasket (often ambiguously called a "garden hose washer") seals the connection against leakage. A variant of this gasket also incorporates a fine-meshed metal or plastic screen to filter out small particles of dirt that may be present in

328-498: 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). This current dependency is not supported by the characteristics shown in the diagram above a certain applied voltage. This is the saturation region , and the JFET is normally operated in this constant-current region where device current

410-462: A common region that minority carriers can move through. A PNP BJT will function like two diodes that share an N-type cathode region, and the NPN like two diodes sharing a P-type anode region. Connecting two diodes with wires will not make a BJT, since minority carriers will not be able to get from one p–n junction to the other through the wire. Both types of BJT function by letting a small current input to

492-406: A few hundred millivolts) biases. For example, in the typical grounded-emitter configuration of an NPN BJT used as a pulldown switch in digital logic, the "off" state never involves a reverse-biased junction because the base voltage never goes below ground; nevertheless the forward bias is close enough to zero that essentially no current flows, so this end of the forward active region can be regarded as

574-454: A flexible hose is connected to a drinkable water supply, the spigot or tap should be fitted with an approved backflow prevention device , to prevent contaminated water from being siphoned back, in the event of a pressure drop. Many water suppliers require this, and plumbing code may legally require permanently installed backflow preventers. Special hoses designed to leak throughout their length are sometimes used to gently distribute water on

656-401: A junction between two regions of different charge carrier concentration. The regions of a BJT are called emitter , base , and collector . A discrete transistor has three leads for connection to these regions. Typically, the emitter region is heavily doped compared to the other two layers, and the collector is doped more lightly (typically ten times lighter ) than the base. By design, most of

738-426: A large input impedance (sometimes on the order of 10  ohms ), little current is drawn from circuits used as input to the gate. A succession of FET-like devices was patented by Julius Lilienfeld in the 1920s and 1930s. However, materials science and fabrication technology would require decades of advances before FETs could actually be manufactured. JFET was first patented by Heinrich Welker in 1945. During

820-502: A lawn or garden. These hoses have either many small holes drilled or punched in them, or are made of a porous material, such as sintered rubber particles. These "soaker hoses" are a simple, low-cost, substitute for a drip irrigation system. These differ from traditional hoses in that the inner membrane expands when filled with water, much like a balloon. An outer cover protects the delicate expandable membrane from punctures. Such hoses "grow" when pressurized, and shrink back down when

902-506: A more positive potential than the n-doped side, and the base–collector junction is reverse biased . When forward bias is applied to the base–emitter junction, the equilibrium between the thermally generated carriers and the repelling electric field of the emitter depletion region is disturbed. This allows thermally excited carriers (electrons in NPNs, holes in PNPs) to inject from the emitter into

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984-591: A niche product at first, with correspondingly high costs. By 2018, these manufacturing issues had been mostly resolved. By then, SiC JFETs were also commonly used in conjunction with conventional low-voltage Silicon MOSFETs. In this combination, SiC JFET + Si MOSFET devices have the advantages of wide band-gap devices as well as the easy gate drive of MOSFETs. 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

1066-425: A patent for a similar device in 1950 termed static induction transistor (SIT). The SIT is a type of JFET with a short channel. High-speed, high-voltage switching with JFETs became technically feasible following the commercial introduction of Silicon carbide (SiC) wide-bandgap devices in 2008. Due to early difficulties in manufacturing — in particular, inconsistencies and low yield — SiC JFETs remained

1148-624: A single crystal of material. The junctions can be made in several different ways, such as changing the doping of the semiconductor material as it is grown, by depositing metal pellets to form alloy junctions, or by such methods as diffusion of n-type and p-type doping substances into the crystal. The superior predictability and performance of junction transistors quickly displaced the original point-contact transistor . Diffused transistors, along with other components, are elements of integrated circuits for analog and digital functions. Hundreds of bipolar junction transistors can be made in one circuit at

1230-423: A thin p-doped region, and a PNP transistor comprises two semiconductor junctions that share a thin n-doped region. N-type means doped with impurities (such as phosphorus or arsenic ) that provide mobile electrons, while p-type means doped with impurities (such as boron ) that provide holes that readily accept electrons. Charge flow in a BJT is due to diffusion of charge carriers (electrons and holes) across

1312-445: A typical garden hose can mate with the female connector on another, which allows multiple garden hoses to be linked end-to-end to increase their overall length. Small rubber or plastic washers (often confusingly called "hose washers") are used in female ends to prevent leakage, because the threads are not tapered and are not used to create a seal. Most garden hoses are not rated for use with hot water; even leaving certain hoses in

1394-563: A very low cost. Bipolar transistor integrated circuits were the main active devices of a generation of mainframe and minicomputers , but most computer systems now use Complementary metal–oxide–semiconductor ( CMOS ) integrated circuits relying on the field-effect transistor (FET). Bipolar transistors are still used for amplification of signals, switching, and in mixed-signal integrated circuits using BiCMOS . Specialized types are used for high voltage switches, for radio-frequency (RF) amplifiers, or for switching high currents. By convention,

1476-414: Is a flexible tube used to convey water . There are a number of common attachments available for the end of the hose, such as sprayers and sprinklers (which are used to concentrate water at one point or to spread it over a large area). Hoses are usually attached to a hose spigot or tap . The alternative term "hosepipe" is a chiefly British, South African, and southern US usage; "hose" or "garden hose"

1558-530: Is a type of transistor that uses both electrons and electron holes as charge carriers . In contrast, a unipolar transistor, such as a field-effect transistor (FET), uses only one kind of charge carrier. A bipolar transistor allows a small current injected at one of its terminals to control a much larger current between the remaining two terminals, making the device capable of amplification or switching . BJTs use two p–n junctions between two semiconductor types, n-type and p-type, which are regions in

1640-724: Is an improvement of the BJT that can handle signals of very high frequencies up to several hundred GHz . It is common in modern ultrafast circuits, mostly RF systems. Two commonly used HBTs are silicon–germanium and aluminum gallium arsenide, though a wide variety of semiconductors may be used for the HBT structure. HBT structures are usually grown by epitaxy techniques like MOCVD and MBE . Bipolar transistors have four distinct regions of operation, defined by BJT junction biases: Although these regions are well defined for sufficiently large applied voltage, they overlap somewhat for small (less than

1722-411: Is called active mode, the base–emitter voltage V BE {\displaystyle V_{\text{BE}}} and collector–base voltage V CB {\displaystyle V_{\text{CB}}} are positive, forward biasing the emitter–base junction and reverse-biasing the collector–base junction. In this mode, electrons are injected from the forward biased n-type emitter region into

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1804-447: Is devoid of majority charge carriers . The depletion region has to be closed to enable current to flow. JFETs can have an n-type or p-type channel. In the n-type, if the voltage applied to the gate is negative with respect to the source, the current will be reduced (similarly in the p-type, if the voltage applied to the gate is positive with respect to the source). Because a JFET in a common source or common drain configuration has

1886-438: Is known colloquially as "garden hose thread" (GHT), but its official designation is NH ("National Hose"): The US standard was defined by NFPA 1963, "Standard for Fire Hose Connections", then later by ANSI-ASME B1.20.7, which specifies 1 + 1 ⁄ 16 inches (27 mm) diameter straight (non-tapered) thread with a pitch of 11.5 threads per inch (TPI). The female thread is abbreviated FHT (for "female hose thread"), and

1968-409: Is made from lightly doped, high-resistivity material. The collector surrounds the emitter region, making it almost impossible for the electrons injected into the base region to escape without being collected, thus making the resulting value of α very close to unity, and so, giving the transistor a large β. A cross-section view of a BJT indicates that the collector–base junction has a much larger area than

2050-447: Is related to V BE {\displaystyle V_{\text{BE}}} exponentially. At room temperature , an increase in V BE {\displaystyle V_{\text{BE}}} by approximately 60 mV increases the emitter current by a factor of 10. Because the base current is approximately proportional to the collector and emitter currents, they vary in the same way. The bipolar point-contact transistor

2132-577: Is reverse biased in normal operation. The reason the emitter is heavily doped is to increase the emitter injection efficiency: the ratio of carriers injected by the emitter to those injected by the base. For high current gain, most of the carriers injected into the emitter–base junction must come from the emitter. The low-performance "lateral" bipolar transistors sometimes used in CMOS processes are sometimes designed symmetrically, that is, with no difference between forward and backward operation. Small changes in

2214-624: Is the predominant term in other English-speaking areas. The term " hose " is also used for other types of flexible, water-carrying tubes such as fire hose used by fire departments . Garden hoses are typically made of extruded synthetic rubber or soft plastic , often reinforced with an internal web of fibers . As a result of these materials, garden hoses are flexible and their smooth exterior facilitates pulling them past trees, posts and other obstacles. Garden hoses are also generally tough enough to survive occasional scraping on rocks and being stepped on, without damage or leaking. Each male end of

2296-408: Is usually 100 or more, but robust circuit designs do not depend on the exact value (for example see op-amp ). The value of this gain for DC signals is referred to as h FE {\displaystyle h_{\text{FE}}} , and the value of this gain for small signals is referred to as h fe {\displaystyle h_{\text{fe}}} . That is, when a small change in

2378-455: Is virtually unaffected by drain-source voltage. The JFET shares this constant-current characteristic with junction transistors and with thermionic tube (valve) tetrodes and pentodes. Constriction of the conducting channel is accomplished using the field effect : a voltage between the gate and the source is applied to reverse bias the gate-source pn-junction, thereby widening the depletion layer of this junction (see top figure), encroaching upon

2460-421: Is zero voltage between its gate and source terminals. If a potential difference of the proper polarity is applied between its gate and source terminals, the JFET will be more resistive to current flow, which means less current would flow in the channel between the source and drain terminals. JFETs are sometimes referred to as depletion-mode devices, as they rely on the principle of a depletion region , which

2542-520: The Ebers–Moll model ) is required. The voltage-control model requires an exponential function to be taken into account, but when it is linearized such that the transistor can be modeled as a transconductance, as in the Ebers–Moll model, design for circuits such as differential amplifiers again becomes a mostly linear problem, so the voltage-control view is often preferred. For translinear circuits , in which

JFET - Misplaced Pages Continue

2624-416: The emitter region, the base region and the collector region. These regions are, respectively, p type, n type and p type in a PNP transistor, and n type, p type and n type in an NPN transistor. Each semiconductor region is connected to a terminal, appropriately labeled: emitter (E), base (B) and collector (C). The base is physically located between the emitter and the collector and

2706-479: The 1940s, researchers John Bardeen , Walter Houser Brattain , and William Shockley were trying to build a FET, but failed in their repeated attempts. They discovered the point-contact transistor in the course of trying to diagnose the reasons for their failures. Following Shockley's theoretical treatment on JFET in 1952, a working practical JFET was made in 1953 by George C. Dacey and Ian M. Ross . Japanese engineers Jun-ichi Nishizawa and Y. Watanabe applied for

2788-401: The BJT collector current is due to the flow of charge carriers injected from a heavily doped emitter into the base where they are minority carriers (electrons in NPNs, holes in PNPs) that diffuse toward the collector, so BJTs are classified as minority-carrier devices . In typical operation, the base–emitter junction is forward biased , which means that the p-doped side of the junction is at

2870-450: The Ebers–Moll model: The base internal current is mainly by diffusion (see Fick's law ) and where The α {\displaystyle \alpha } and forward β {\displaystyle \beta } parameters are as described previously. A reverse β {\displaystyle \beta } is sometimes included in the model. The unapproximated Ebers–Moll equations used to describe

2952-462: The FET from drain to source at any (permissible) drain-to-source voltage (see, e. g., the I – V characteristics diagram above). In the saturation region , the JFET drain current is most significantly affected by the gate–source voltage and barely affected by the drain–source voltage. If the channel doping is uniform, such that the depletion region thickness will grow in proportion to the square root of

3034-635: The MOSFET, as well as lower flicker noise , and is therefore used in some low- noise , high input-impedance op-amps . Additionally the JFET is less susceptible to damage from static charge buildup. The current in N-JFET due to a small voltage V DS (that is, in the linear or ohmic or triode region ) is given by treating the channel as a rectangular bar of material of electrical conductivity q N d μ n {\displaystyle qN_{d}\mu _{n}} : where Then

3116-631: The absolute value of the gate–source voltage, then the channel thickness b can be expressed in terms of the zero-bias channel thickness a as where The transconductance for the junction FET is given by where V P {\displaystyle V_{\text{P}}} is the pinchoff voltage, and I DSS is the maximum drain current. This is also called g fs {\displaystyle g_{\text{fs}}} or y fs {\displaystyle y_{\text{fs}}} (for transadmittance ). Bipolar junction transistors A bipolar junction transistor ( BJT )

3198-427: The absorption of photons , and handles the dynamics of turn-off, or recovery time, which depends on charge in the base region recombining. However, because base charge is not a signal that is visible at the terminals, the current- and voltage-control views are generally used in circuit design and analysis. In analog circuit design, the current-control view is sometimes used because it is approximately linear. That is,

3280-422: The advantage of interconnecting without distinction between "male" and "female" connectors, Some connectors also incorporate an "autostop" feature. This is an internal valve which is shut off by water pressure, and it is opened only by connecting a fitting or appliance; thus, disconnecting a hose fitted with this adaptor will automatically stop the flow of water. This eases connecting and changing appliances without

3362-480: The arrow points from P to N, the direction of conventional current when forward-biased. An English mnemonic is that the arrow of an N-channel device "points i n ". 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 gain ( transconductance ) than

JFET - Misplaced Pages Continue

3444-400: The base and reach the collector is a measure of the BJT efficiency. The heavy doping of the emitter region and light doping of the base region causes many more electrons to be injected from the emitter into the base than holes to be injected from the base into the emitter. A thin and lightly doped base region means that most of the minority carriers that are injected into the base will diffuse to

3526-465: The base control an amplified output from the collector. The result is that the BJT makes a good switch that is controlled by its base input. The BJT also makes a good amplifier, since it can multiply a weak input signal to about 100 times its original strength. Networks of BJTs are used to make powerful amplifiers with many different applications. In the discussion below, focus is on the NPN BJT. In what

3608-427: The base reduce the BJT gain. Another useful characteristic is the common-base current gain , α F . The common-base current gain is approximately the gain of current from emitter to collector in the forward-active region. This ratio usually has a value close to unity; between 0.980 and 0.998. It is less than unity due to recombination of charge carriers as they cross the base region. Alpha and beta are related by

3690-400: The base region. These carriers create a diffusion current through the base from the region of high concentration near the emitter toward the region of low concentration near the collector. To minimize the fraction of carriers that recombine before reaching the collector–base junction, the transistor's base region must be thin enough that carriers can diffuse across it in much less time than

3772-434: The base–emitter junction and recombination in the base). In many designs beta is assumed high enough so that base current has a negligible effect on the circuit. In some circuits (generally switching circuits), sufficient base current is supplied so that even the lowest beta value a particular device may have will still allow the required collector current to flow. BJTs consists of three differently doped semiconductor regions:

3854-467: The characteristics allows designs to be created following a logical process. Bipolar transistors, and particularly power transistors, have long base-storage times when they are driven into saturation; the base storage limits turn-off time in switching applications. A Baker clamp can prevent the transistor from heavily saturating, which reduces the amount of charge stored in the base and thus improves switching time. The proportion of carriers able to cross

3936-507: The collector and not recombine. The common-emitter current gain is represented by β F or the h -parameter h FE ; it is approximately the ratio of the collector's direct current to the base's direct current in forward-active region. (The F subscript is used to indicate the forward-active mode of operation.) It is typically greater than 50 for small-signal transistors, but can be smaller in transistors designed for high-power applications. Both injection efficiency and recombination in

4018-405: The collector current is approximately β F {\displaystyle \beta _{\text{F}}} times the base current. Some basic circuits can be designed by assuming that the base–emitter voltage is approximately constant and that collector current is β times the base current. However, to accurately and reliably design production BJT circuits, the voltage-control model (e.g.

4100-458: The collector–base depletion region, are swept into the collector by the electric field in the depletion region. The thin shared base and asymmetric collector–emitter doping are what differentiates a bipolar transistor from two separate diodes connected in series. The collector–emitter current can be viewed as being controlled by the base–emitter current (current control), or by the base–emitter voltage (voltage control). These views are related by

4182-466: The collector–base voltage, for example, causes a greater reverse bias across the collector–base junction, increasing the collector–base depletion region width, and decreasing the width of the base. This variation in base width often is called the Early effect after its discoverer James M. Early . Narrowing of the base width has two consequences: Both factors increase the collector or "output" current of

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4264-555: The conducting channel and restricting its cross-sectional area. The depletion layer is so-called because it is depleted of mobile carriers and so is electrically non-conducting for practical purposes. When the depletion layer spans the width of the conduction channel, pinch-off is achieved and drain-to-source conduction stops. Pinch-off occurs at a particular reverse bias ( V GS ) of the gate–source junction. The pinch-off voltage (V p ) (also known as threshold voltage or cut-off voltage ) varies considerably, even among devices of

4346-465: The conventional direction, but labels for the movement of holes and electrons show their actual direction inside the transistor. The arrow on the symbol for bipolar transistors indicates the p–n junction between base and emitter and points in the direction in which conventional current travels. BJTs exist as PNP and NPN types, based on the doping types of the three main terminal regions. An NPN transistor comprises two semiconductor junctions that share

4428-508: The currents occurs, and sufficient time has passed for the new condition to reach a steady state h fe {\displaystyle h_{\text{fe}}} is the ratio of the change in collector current to the change in base current. The symbol β {\displaystyle \beta } is used for both h FE {\displaystyle h_{\text{FE}}} and h fe {\displaystyle h_{\text{fe}}} . The emitter current

4510-402: The current–voltage relation of the base–emitter junction, which is the usual exponential current–voltage curve of a p–n junction (diode). The explanation for collector current is the concentration gradient of minority carriers in the base region. Due to low-level injection (in which there are much fewer excess carriers than normal majority carriers) the ambipolar transport rates (in which

4592-476: The cutoff region. The diagram shows a schematic representation of an NPN transistor connected to two voltage sources. (The same description applies to a PNP transistor with reversed directions of current flow and applied voltage.) This applied voltage causes the lower p–n junction to become forward biased, allowing a flow of electrons from the emitter into the base. In active mode, the electric field existing between base and collector (caused by V CE ) will cause

4674-672: The design of digital integrated circuits. The incidental low performance BJTs inherent in CMOS ICs, however, are often utilized as bandgap voltage reference , silicon bandgap temperature sensor and to handle electrostatic discharge . The germanium transistor was more common in the 1950s and 1960s but has a greater tendency to exhibit thermal runaway . Since germanium p-n junctions have a lower forward bias than silicon, germanium transistors turn on at lower voltage. Various methods of manufacturing bipolar transistors were developed. BJTs can be thought of as two diodes (p–n junctions) sharing

4756-511: The direction of current on diagrams is shown as the direction that a positive charge would move. This is called conventional current . However, current in metal conductors is generally due to the flow of electrons. Because electrons carry a negative charge, they move in the direction opposite to conventional current. On the other hand, inside a bipolar transistor, currents can be composed of both positively charged holes and negatively charged electrons. In this article, current arrows are shown in

4838-432: The drain current in the linear region can be approximated as In terms of I DSS {\displaystyle I_{\text{DSS}}} , the drain current can be expressed as The drain current in the saturation or active or pinch-off region is often approximated in terms of gate bias as where I DSS is the saturation current at zero gate–source voltage, i.e. the maximum current that can flow through

4920-416: The emitter–base junction. The bipolar junction transistor, unlike other transistors, is usually not a symmetrical device. This means that interchanging the collector and the emitter makes the transistor leave the forward active mode and start to operate in reverse mode. Because the transistor's internal structure is usually optimized for forward-mode operation, interchanging the collector and the emitter makes

5002-479: The excess majority and minority carriers flow at the same rate) is in effect determined by the excess minority carriers. Detailed transistor models of transistor action, such as the Gummel–Poon model , account for the distribution of this charge explicitly to explain transistor behaviour more exactly. The charge-control view easily handles phototransistors , where minority carriers in the base region are created by

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5084-414: The exponential I–V curve is key to the operation, the transistors are usually modeled as voltage-controlled current sources whose transconductance is proportional to their collector current. In general, transistor-level circuit analysis is performed using SPICE or a comparable analog-circuit simulator, so mathematical model complexity is usually not of much concern to the designer, but a simplified view of

5166-442: The flowing stream of water. The purpose of this filter is to intercept debris which could otherwise clog the small openings used to disperse a spray of water from various garden sprayers and sprinklers. Adaptors made of metal or plastic are available to interconnect GHT, BSP, NPT , hose barb , and quick-connect fittings. In the 1980s, the use of quick-connector systems became increasingly popular. These are fittings that attach to

5248-410: The following identities: Beta is a convenient figure of merit to describe the performance of a bipolar transistor, but is not a fundamental physical property of the device. Bipolar transistors can be considered voltage-controlled devices (fundamentally the collector current is controlled by the base–emitter voltage; the base current could be considered a defect and is controlled by the characteristics of

5330-512: The hose and or screw into common hose connectors and equipment, allowing hoses and accessories to be easily connected together using a snap-fit type system. The first plastic connector was invented in the UK by Hozelock in 1959, and the style has now become a de facto standard throughout Europe and the wider world, compatible with and imitated by many other manufacturers. A differently-designed hermaphroditic quick-connect hose fitting made by GEKA has

5412-497: The inner surface of the hose. Clinical cases of Legionnaires' disease or Pontiac fever have been found to be associated with inhalation of garden hose aerosols containing Legionella bacteria. The report provided measured microbial densities resulting from controlled hose conditions in order to quantify the human health risks. The densities of Legionella spp. identified in two types of hoses were found to be similar to those reported during legionellosis outbreaks from other causes. It

5494-400: The majority of these electrons to cross the upper p–n junction into the collector to form the collector current I C . The remainder of the electrons recombine with holes, the majority carriers in the base, making a current through the base connection to form the base current, I B . As shown in the diagram, the emitter current, I E , is the total transistor current, which is the sum of

5576-431: The male part is abbreviated MHT (for "male hose thread"). This fitting is used with 1 ⁄ 2 -inch, 5 ⁄ 8 -inch, and 3 ⁄ 4 -inch hoses. In other countries, a British Standard Pipe (BSP) thread is used, which is 3 ⁄ 4 inch (19 mm) and 14 TPI (male part outside diameter is 26.441 mm or 1.04 in). The GHT and BSP standards are not compatible, and attempting to connect

5658-412: The need to shut off the water first. In 2014, it was reported that use of common garden hoses in combination with spray nozzles may generate aerosols containing droplets smaller than 10 μm, which can be inhaled by nearby people. Water stagnating in a hose between uses, especially when warmed by the sun, can host the growth and interaction of Legionella and free-living amoebae (FLA) as biofilms on

5740-469: The other terminal currents, (i.e. I E  =  I B  +  I C ). In the diagram, the arrows representing current point in the direction of conventional current – the flow of electrons is in the opposite direction of the arrows because electrons carry negative electric charge . In active mode, the ratio of the collector current to the base current is called the DC current gain . This gain

5822-470: The p-type base where they diffuse as minority carriers to the reverse-biased n-type collector and are swept away by the electric field in the reverse-biased collector–base junction. For an illustration of forward and reverse bias, see semiconductor diodes . In 1954, Jewell James Ebers and John L. Moll introduced their mathematical model of transistor currents: The DC emitter and collector currents in active mode are well modeled by an approximation to

5904-473: The pressure is released, allowing for easier storage. Garden hoses connect using a male/female thread connection. The technical term for this arrangement is a "hose union ". Spigots or sillcocks have male hose connectors only, and the mating end of a hose has a captive nut which fits the threads there. The thread standard for garden hose connectors in the United States, its territories, and Canada

5986-463: The same type. For example, V GS(off) for the Temic J202 device varies from −0.8 V to −4 V . Typical values vary from −0.3 V to −10 V . (Confusingly, the term pinch-off voltage is also used to refer to the V DS value that separates the linear and saturation regions.) To switch off an n -channel device requires a n egative gate–source voltage ( V GS ). Conversely, to switch off

6068-421: The semiconductor's minority-carrier lifetime. Having a lightly doped base ensures recombination rates are low. In particular, the thickness of the base must be much less than the diffusion length of the carriers. The collector–base junction is reverse-biased, and so negligible carrier injection occurs from the collector to the base, but carriers that are injected into the base from the emitter, and diffuse to reach

6150-418: The source (S) and the 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 operation can be compared to that of a garden hose . The flow of water through a hose can be controlled by squeezing it to reduce the cross section and the flow of electric charge through

6232-673: The sun while pressurized can cause them to burst. Hoses used to carry potable water are typically made of NSF International -listed polymers tested and shown not to leach harmful materials into the drinking water, such as the plasticizers ( phthalates ) used in polyvinyl chloride (PVC, or vinyl) hoses. As implied by the name, garden hoses are commonly used to transport water for gardening, lawn care, and other landscaping purposes. They are also used for outdoor cleaning of items such as vehicles, equipment, building exteriors, and animals. NSF-approved hoses may be used for connecting drinkable water to recreational vehicles and trailers. Whenever

6314-466: The symbol should be used only for those JFETs where they are indeed interchangeable. The symbol may be drawn inside a circle (representing the envelope of a discrete device) if the enclosure is important to circuit function, such as dual matched components in the same package. In every case the arrow head shows the polarity of the P–N junction formed between the channel and the gate. As with an ordinary diode ,

6396-417: The three currents in any operating region are given below. These equations are based on the transport model for a bipolar junction transistor. where As the collector–base voltage ( V CB = V CE − V BE {\displaystyle V_{\text{CB}}=V_{\text{CE}}-V_{\text{BE}}} ) varies, the collector–base depletion region varies in size. An increase in

6478-423: The transistor in response to an increase in the collector–base voltage. When the base–collector voltage reaches a certain (device-specific) value, the base–collector depletion region boundary meets the base–emitter depletion region boundary. When in this state the transistor effectively has no base. The device thus loses all gain when in this state. Garden hose A garden hose , hosepipe , or simply hose

6560-428: The values of α and β in reverse operation much smaller than those in forward operation; often the α of the reverse mode is lower than 0.5. The lack of symmetry is primarily due to the doping ratios of the emitter and the collector. The emitter is heavily doped, while the collector is lightly doped, allowing a large reverse bias voltage to be applied before the collector–base junction breaks down. The collector–base junction

6642-670: The voltage applied across the base–emitter terminals cause the current between the emitter and the collector to change significantly. This effect can be used to amplify the input voltage or current. BJTs can be thought of as voltage-controlled current sources , but are more simply characterized as current-controlled current sources, or current amplifiers, due to the low impedance at the base. Early transistors were made from germanium but most modern BJTs are made from silicon . A significant minority are also now made from gallium arsenide , especially for very high speed applications (see HBT, below). The heterojunction bipolar transistor (HBT)

6724-555: Was invented in December 1947 at the Bell Telephone Laboratories by John Bardeen and Walter Brattain under the direction of William Shockley . The junction version known as the bipolar junction transistor (BJT), invented by Shockley in 1948, was for three decades the device of choice in the design of discrete and integrated circuits . Nowadays, the use of the BJT has declined in favor of CMOS technology in

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