Phenomenon - fet operation, Electrical Engineering

Phenomenon - Fet operation:

For either improvement- or depletion-mode devices, at drain-to-source voltages very much less than gate-to-source voltages, changing the gate voltage will change the channel resistance, drain current will be proportional to drain voltage (referenced to source voltage). In this type of mode the FET operates such as a variable resistor and the FET is said to be operating in a linear modeor ohmic mode.

If drain-to-source voltage is gets increased, this creates a important asymmetrical change in the shape of the channel because of a gradient of voltage potential from source to drain. The shape of the inversion region turns "pinched-off" near the drain end of the channel. If drain-to-source voltage is raised further, the pinch-off point of the channel starts to move away from the drain in the direction of the source. The FET is supposed to be in saturation mode; a number of authors refer to it as active mode, for a better analogy along with bipolar transistor operating regions. The saturation mode, or the region in between the ohmic and saturation, is employed while amplification is required. The in-between region is occasionally considered to be part of the ohmic or linear region, even in which drain current is not approximately linear with drain voltage.

Although the conductive channel made by gate-to-source voltage no longer connects source to drain throughout saturation mode, from flowing the carriers are not blocked. Considering once again an n-channel device, a depletion region available in the p-type body that surrounding the conductive channel and drain and source regions. The electrons that have the channel are free to move out of the channel by the depletion region if attracted to the drain through drain-to-source voltage. The carriers' depletion region is free and comprises a resistance identical to silicon. Any type of rise of the drain-to-source voltage will increase the distance from drain to the pinch-off point, increasing resistance because of the depletion region proportionally to the applied drain-to-source voltage. This proportional change results in the drain-to-source current to remain comparatively fixed independent of changes to the drain-to-source voltage and quite different the linear mode operation. So in saturation mode, the FET acts like a constant-current source rather than like a resistor and can be used most efficiently as a voltage amplifier. In this type of case, the gate-to-source voltage ascertains the level of constant current by the channel.

Posted Date: 1/11/2013 4:50:02 AM | Location : United States







Related Discussions:- Phenomenon - fet operation, Assignment Help, Ask Question on Phenomenon - fet operation, Get Answer, Expert's Help, Phenomenon - fet operation Discussions

Write discussion on Phenomenon - fet operation
Your posts are moderated
Related Questions
Meter Field Testing and Installation Practices Here, we discuss the installation, commissioning and field testing of meters. Energy Meters - Installation and Commissionin

Electric circuits or networks are formed by interconnecting various devices, sources, and components. Although the effects of each element (such as heating effects, electric-?eld e


Q. Three identical single-phase transformers are to be connected to form a three-phase bank rated at 300 MVA, 230:34.5 kV. For the following configurations, determine the voltage,

Q. Frequency stability of quartz crystals ? The amount of frequency deviation from the ambient temperature frequency over the operating temperature range. This deviation is ass

Q. A depletion MOSFET is given to have large V A , V P = 2.8V, I DSS = 4.3 mA, v DS = 4.5V,and v GS = 1.2V. (a) Is theMOSFEToperating in the active region? (b) Find iD.

IGBT ( Insulated Gate Bipolar Transistor ) IGBT  stands for  insulated gate bipolar transistor. It is having the advantages of both power MOSFET and BJT.  In IGBT  layer is P

why the primary bushing of 7970/13.8 distribution transformer blown up when connected wye on a 13.8 kv source?

DC Motor Starting When voltage is applied to the armature of a dcmotorwith the rotor stationary, no emf is generated and the armature current is limited only by the internal ar

Q A residence is supplied with a voltage v(t) = 110√2cos120πt Vand a current i(t) = 10√2cos120πt A. If an electricmeter is used tomeasure the average power, find the meter reading,