IGBT-Insulated Gate Bipolar Transistors

jojo September 8, 2009 5 Comments
Introduction to IGBT-Insulated Gate Bipolar Transistors Insulated gate bipolar transistor (IGBT) is a new high conductance MOS gate-controlled power switch. The fabrication process is similar to that of an N-channel power MOSFET but employs an N-epitaxial layer grown on a P+ substrate. In operation the epitaxial region is conductivity modulated (by excess holes and electrons) thereby eliminating a major component of the on-resistance. For example, on-resistance values have been reduced by a factor of about 10 compared with those...
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V-FET or Power Mosfets

jojo September 7, 2009 3 Comments
Power MOSFETs are usually constructed in V-configuration, as shown in figure. That is why, the device is sometimes called the V-MOSFET or V-FET. V-shaped cut penetrates from the device surface almost to the N+ substrate through N+, P and N~ layers, as seen from figure. The N+ layers are heavily doped, low resistive material, while the N~ layer is a lightly doped, high-resistance region. The silicon dioxide dielectric layer covers both the horizontal surface and V-cut surface. The insulated...
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Dual Gate Mosfets

jojo September 7, 2009 No Comments
Cross-view of a dual-gate N-channel depletion type MOSFET is shown in figure. It acts as if two FETs are connected in series, as is obvious from figure. The middle block acts as drain for unit no 1 and source for unit no 2. Thus the current flow through the MOSFET is controlled by the voltage of both the gates. Drain current ID can be cut­off by making either gate sufficiently negative.

EMOSFET-Enhancement MOSFET

jojo August 31, 2009 3 Comments
Although DE-MOSFET is useful in special applications, it does not enjoy widespread use. However, it played an important role in history because it was part of the evolution towards the E-mode MOSFET, a device that has revolutionized the electronic industry. E-MOSFET has become enormously important, in digital electronics and. In the absence of E-MOSFET’s the personal computers (PCs) that are now so widespread would not exist. Construction of an EMOSFET: Figure shows the construction of an N-channel E-MOSFET. The...
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DEMOSFET-Depletion Enhancement MOSFET

jojo April 23, 2012 9 Comments
We know that when the gate is biased negative with respect to the source in an N-channel JFET, the depletion region widths are increased. Theincrease in the depletion regions reduces the channel thickness, which increases its resistance. The net result is that drain current ID is reduced. If the polarity of VGG were reversed so as to apply a positive bias to the gate with respect to source, the P-N junctions between the gate and the channel would then...
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MOSFET-Metal Oxide Semiconductor Transistor

jojo April 23, 2012 2 Comments
Introduction to MOSFET-Metal Oxide Semiconductor Field Effect Transistor, Metal-oxide-semiconductor field-effect transistor (MOSFET) is an important semiconductor device and is widely employed in many circuit applications. Since it is constructed with the gate terminal insulated from the channel, it is sometimes called insulated gate FET (IGFET). Like, a JFET, a MOSFET is also a three terminal (source, gate and drain) device and drain current in it is also controlled by gate bias. The operation of MOSFET is similar to that...
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FET biasing

jojo August 31, 2009 1 Comment
Unlike BJTs, thermal runaway does not occur with FETs, as already discussed in our blog. However, the wide differences in maximum and minimum transfer characteristics make ID levels unpredictable with simple fixed-gate bias voltage. To obtain reasonable limits on quiescent drain currents ID and drain-source voltage VDS, source resistor and potential divider bias techniques must be used. With few exceptions, MOSFET bias circuits are similar to those used for JFETs. Various FET biasing circuits are discussed below: Fixed Bias....
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Simple FET Amplifier

john August 28, 2009 2 Comments
From the circuit named “looking into the drain” of the FET it is seen (for small signal operation) an equivalent circuit consisting of two generators in series, one of – u times the gate signal voltage Vin and the second (u + 1) times the source-signal voltage Vs and the resistance rd + ((a + 1) RG. Note that the source-signal voltage Vs and the resistance in the source lead are both multiplied by the same factor, (u +...
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Characteristics of JFETS

jojo August 28, 2018 5 Comments
You may also like : Field Effect Transistors (FET) and JFET-Junction Field Effect Transistors What is a Junction Field Effect Transistor? A JFET is a semiconductor with 3 terminals, available either in N-channel or P-channel types. It is unipolar but has similar characteristics as of its Bipolar cousins. Instead of PN junctions, a JFET uses an N-type or P-type semiconductor material between the collector and emitter (Source & Drain). The N-type material is made by doping Silicon with donor...
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JFET-Junction Field Effect Transistor

jojo August 4, 2017 5 Comments
As already mentioned in Field Effect Transistors (FET) , JFET’s are of two types, namely N-channel JFETs and P-channel JFETs. Generally N-channel JFETs are more preferred than P-channel. N-channel and P-channel JFETs are shown in the figures below. Basic Construction. The structure is quite simple. In an N-channel JFET an N-type silicon bar, referred to as the channel, has two smaller pieces of P-type silicon material diffused on the opposite sides of its middle part, forming P-N junctions, as illustrated...
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