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 […]
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
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
DE-MOSFET can be operated either with positive or negative gate, so its operating or quiescent point can be set at VGS = 0, as illustrated in figure. In figure the gate G is at ground potential for dc since ac signal source appears to be short-circuited for dc and sets Q-point at VGS = 0.
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
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
FET is a device that is usually operated in the constant-current portion of its output characteristics. But if it is operated on the region prior to pinch-off (that is where VDS is small, say below 100 mV), it will behave as a voltage-variable resistor (WE). It is due to the fact that in this region
What is FET (Field Effect Transistor) FET, also called unipolar transistor is a transistor used to control the electrical behaviour of a device. FET has a very high input impedance (100 Mega ohm in case of JFETs and 104 to 109 Mega Ohm in case of MOSFETs), the major shortcomings of an ordinary transistor i.e.
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
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 +
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).
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
Series Inductor Filter. In this arrangeÂment a high value inductor or choke L is connected in series with the rectifier element and the load, as illustrated in figure. The filtering action of an inductor filter deÂpends upon its property of opposing any change in the current flowing through it. When the output
The drawbacks of pi-filters are the comparatively larger cost, more weight, bigger size and external field developed by the series inductor. However, these drawbacks can be overcome by replacing the series inductor by a series resistor R. Such a circuit is called the R-C filter circuit and is given in figure. By deliberate design R
Introduction to FET-Field Effect Transistor So far we have discussed the circuit applications of ordinary transistors, in which both holes and electrons take part. This is the reason that these are sometimes called the bipolar transistors. Such transistors have two main drawbacks namely low input impedance because of forward biased emitter junction and considerable noise
A simple series inductor reduces both the peakand effective values of the output current and output voltage. On the other hand a simple shunt capacitor filter reduces the ripple voltage but increases the diode current. The diode may get damaged due to large current and at the same time it causes greater heating of supply
Shunt Capacitor Filter and types of it: This is the most simple form of the filter circuit and in this arrangement a high value capacitor C is placed directly across the output terminals, as shown in figure. During the conduction period it gets charged and stores up energy to it during non-conduction period. Through this process,
We have learnt in rectifier circuits about converting a sinusoidal ac voltage into its corresponding pulsating dc. Apart from the dc component, this pulsating dc voltage will have unwanted ac components like the components of its supply frequency along with its harmonics (together called ripples). These ripples will be the highest for a single-phase half
Polyphase rectifier In polyphase rectifier we will be discussing in detail the working, the input and the output wave forms of a three phase half wave rectifier and three phase full wave rectifier, along with the connections of an interface transformer on a 6-diode rectifier. Three phase Half Wave Rectifier A three phase half wave
A Full-wave rectifier is a circuit arrangement that makes use of both half cycles of input alternating current (AC) and converts them to direct current (DC). In our tutorial on Half-wave rectifiers, we have seen that a half-wave rectifier makes use of only one-half cycle of the input alternating current. Thus a full-wave rectifier is
Centre-Tap Full Wave Rectifier We have already discussed the Full Wave Bridge Rectifier, which uses four diodes, arranged as a bridge, to convert the input alternating current (AC) in both half cycles to direct current (DC). In the case of centre-tap full wave rectifier, only two diodes are used, and are connected to the opposite
A simple Half Wave Rectifier is nothing more than a single pn junction diode connected in series to the load resistor. As you know a diode is to electric current like a one-way valve is to water, it allows electric current to flow in only one direction. This property of the diode is very useful
Photo-diode is a two-terminal semiconductor P-N junction device and is designed to operate with reverse bias. The basic biasing arrangement, construction and symbols for the device are given in figure. It is either mounted in translucent case or has its semiconductor junction mounted beneath an optical lens. The output voltÂage is taken from across a
Class D power amplifier. Class D power amplifier is a type of audio amplifier were the power handling devices are operated as binary switches. Since the power handling devices (MOSFETS) works as perfect binary switches, no time is wasted in between the transition of stages and no power is wasted in the zero input condition.
Class C power amplifier. Class C power amplifier is a type of amplifier where the active element (transistor) conduct for less than one half cycle of the input signal. Less than one half cycle means the conduction angle is less than 180° and its typical value is 80° to 120°. The reduced conduction angle improves
