How can a jfet be used as a constant current source, Electrical Engineering

Assignment Help:

Q. How can a JFET be used as a constant current source? Explain from the drain characteristics.

As the VDS voltage is increased from 0 to a few volts, the current will increase as determined by ohm's law and the plot of ID versus VDS will appear as shown below.

2258_How can a JFET be used as a constant current source.png


The relative straightness of the graph reveals that for the region of low voltage level referred to as  VP. The depletion region will widen, causing a noticeable reduction in the channel width. The reduced path of conduction causes the resistance to increase and the curve in the graph to occur. The more horizontal the curve the more the resistance, suggesting that the resistance is approaching infinite ohms. If VDS is increased to a level where it appears that the two depletion regions will touch. A condition known as pinch off will result. The level of VDS that establishes this condition is referred to as pinch off voltage. The term pinch off is a misnomer which actually means that the value of ID has become 0 A. this is hardly the case as the ID still maintains a saturation level defined as IDSS. In reality a very narrow channel still exists, with a current of very high density. The fact that ID does not drop off to 0 at pinch-off and maintains a saturation level is verified by the fact : the absence of the drain current would remove the possibility of different potential levels through out the n channel material to establish the varying levels of reverse bias along the p-n junction. The result would be a loss of depletion region distribution that caused pinch off in the first place.

The fact about the constant current IDSS can be used to make a JFET a constant current source as its current value remain constant. The JFET is thus a very versatile device and can be used  as a current source with much stabler characteristics than a zener diode current regulator.


Related Discussions:- How can a jfet be used as a constant current source

Explain the principle of a thermocouple, Explain the principle of a thermoc...

Explain the principle of a thermocouple. Give two examples of some common thermocouples. Thermocouples : They are used for the measurement of temperature. While two wires of v

Working of a linear variable differential transformer, Illustrate the const...

Illustrate the construction and principle of working of a linear variable differential transformer. Describe how the magnitude and direction of displacement of core of LVDT is dete

Strategic perspective of an organization, Strategic Perspective of An organ...

Strategic Perspective of An organization Strategic perspectives cover functions such as revenue, customer satisfaction, people, procedure and technology. Every organization re

Doping, expalin process of doping how to do doping

expalin process of doping how to do doping

Explain the different instruction formats, Explain the different instructio...

Explain the different instruction formats with examples The instruction set is grouped into the following formats One byte instruction MOV C,A Two byte instruction

Define resistance strain gauge, Q. Define Resistance Strain Gauge? Mech...

Q. Define Resistance Strain Gauge? Mechanical and civil engineers routinely employ the dependence of resistance on the physical dimensions of a conductor to measure strain. A s

For which type of measurement thermocouples are used, Thermocouples are use...

Thermocouples are used for the measurement of (A)  Humidity.                                   (B) Pressure. (C) Temperature.                               (D) Density.

Self-inductance and the induced e.m.f, Self-inductance and the induced e.m....

Self-inductance and the induced e.m.f Inductance is the name given to the property of a circuit whereby there is an e.m.f induced into the circuit by alter of flux linkages pro

Higher order address bus - pins and signals , Higher order  Address Bus ...

Higher order  Address Bus The 8085 microprocessor  has 8 pins  dedicated to higher order address A15 - A8. These pins  are used to connect  higher  order address bus. These  p

Write Your Message!

Captcha
Free Assignment Quote

Assured A++ Grade

Get guaranteed satisfaction & time on delivery in every assignment order you paid with us! We ensure premium quality solution document along with free turntin report!

All rights reserved! Copyrights ©2019-2020 ExpertsMind IT Educational Pvt Ltd