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McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.


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(Field Effect Transistor) One of two major categories of transistor; the other is bipolar. FETs use a gate element that, when charged, creates an electromagnetic field that changes the conductivity of a silicon channel and turns the transistor on or off. FETs are fabricated as individually packaged discrete components as well as by the hundreds of millions on a single chip.

FETs vs. Bipolar
FET-based silcon chips are easier to construct than their bipolar counterparts. FETs switch a little slower than bipolar transistors, but use less power. Once the gate terminal on an FET has been charged, no more current is needed to keep that transistor on (closed) for the duration of time required. By comparison, a bipolar transistor requires a small amount of current flowing to keep the transistor on. While the current for one transistor may be negligible, it adds up when millions are switching simultaneously. The heat dissipated on bipolar limits the total number of transistors that can be built on the chip, which is why CMOS logic (based on FETs) is used to build chips with millions of transistors.

The most widely used and widely known FETs are MOSFETs (metal oxide semiconductor FETs), which come in NMOS (n-channel) and PMOS (p-channel) varieties. On a chip, NMOS and PMOS transistors are wired together in a complementary fashion to create CMOS logic, which is the most predominant and used in almost every electronic device today. See MOSFET and n-type silicon.

There Are Many Kinds of FETs
Similar to MOSFETs are JFETs (junction FETs), which use a PN junction gate rather than a poly-crystalline gate. Used for microwave communications, MESFETs (metal semiconductor FETs) are similar to JFETs, but use a Schottky metal gate and are made from gallium arsenide or indium phosphide, not silicon. Evolving from MESFETs for higher-frequency applications are HEMTs and PHEMTs (high electron mobility transistors and pseudomorphic high electron mobility transistors). HEMTs are also called MODFETs, TEGFETs and SDHTs (modulation doped FETs, two-dimensional electron gas FETs and selectively doped heterojunction transistors).

Another high-frequency FET is the gallium arsenide-based CHFET (complementary heterostructure FET), which uses a complementary architecture similar to CMOS.

FETs vs. Bipolar
After the gate is charged in an FET, no more current flows, but the transistor remains closed (turned on) during the required time period. Bipolar transistors (BJTs) require current the entire time the transistor must be closed.
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This report provides a detailed manufacturing cost analysis of the JFET, the MOSFET and the package as well as the estimated selling price of each one of the five cascode components.
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One is left to wonder--if they used the standard, high performance topology in this op amp, why did they use the simple JFET stage in the first op amp?
voltage (V) [3] (a) -- [+ or -] 5 [4] Unspecified [+ or -] 5 level 3 CMOS model [5] (b) Unspecified [+ or -] 5 CMOS model [6] (b) Unspecified [+ or -] 5 CMOS model [7] TSMC 0.25 [+ or -] 1.5 [micro]m CMOS model [8] circuit IBM 0.13 [+ or -] 0.75 1 [micro]m SIGE013 CMOS [8] circuit IBM 0.13 [+ or -] 0.75 2 [micro]m SIGE013 CMOS [9] IBM 0.13 [+ or -] 0.75 [micro]m SIGE013 CMOS [10] HF3CMOS [+ or -] 2.5 BJT model [11] ALA400-CBIC-R [+ or -] 1.5 BJT model [12] (b) 2N5485 N-Channel -- RF JFET and AD844 PSPICE models This work IBM 0.13 [micro]m -[V.sub.TP] SIGE013 CMOS and--[V.sub.TN] Criterion\ Total Maximum power Ref.
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GaAs LSI devices and eventually LSI logic circuits, based on either JFET or MESFET technology, should be capable of operating up to about [10.sup.15 N/cm.sup.2] without suffering failure or significant performance degradation.
There are many types of FETs, including the MOSFET (metal-oxide-semiconductor), MESFET (metal-semiconductor), JFET (junction), OFET (organic), GNRFET (graphene nano-ribbon), and CNTFET (carbon nanotube).
The conduction losses of the power MOSFET of this era were primarily determined by the channel density, JFET resistance and epitaxial resistance (See Figure 1).
SITs are a class of transistors with a short channel JFET structure in which the current, flowing vertically between the source and drain, is controlled by the height of an electrostatically induced potential energy barrier under the source.