9.3 Sspd_chapter 7_part 3_basic electrical properties of mos and

SSPD_Chapter 7_Part 3 gives the basic elecrical properties of MOS devices.

SSPD_Chapter 7_Part 3_Basic Electrical Properties of MOS and MOS circuits.

7.3 The Output Characteristics of (Depletion)n-channel MOSFET.

Field Effect Transistors cover JFET and MOSFET. The underlying principle of FET is that there is a conducting channel which obeys Ohm’s Law:

Where

L = lemgth of the channel and A = cross-sectional area as shown in Figure 7.3.1.

And ρ = resistivity = 1/σ = 1/conductivity = 1/(qµ n n);

Here q = charge of an electron, µ n = mobility of an electron in the channel and n = conducting electron density in the n-channel.

Generally the n-channel is like a 2-D sheet hence its mobility is much lower than that in 3-D bulk. Typically µ n = 1450 cm 2 /(V-sec) in Bulk Semiconductor and 650 cm 2 /(V-sec) in the channel in FET.

.

As can be seen in the Figure 7.3.1 in n-channel FET electrons are being sourced from the source end and being drained out from the drain end. By corollary in p-channel FET holes will be sourced and holes will be drained out. This is the reason why the symbols are shown with the arrow of the conventional current flow. In nMOSFET conventional current is shown to come out of the Source and in pMOSFET conventional current is shown to enter into the Source as shown in Figure 7.3.2.

Equation 7.3.1 is a linear equation with I-V characterisyics as shown in Figure 7.3.3.

As seen in the Figure 7.3.3, I-V is linear for the whole range of voltage applied and is anti-symmetrical about the y-axis. Hence n-channel is a bilateral device where for positive voltage positive current flows and for negative voltage negative current flows with equal ease.

7.3.1. FET as a 3-terminal Device in Ohmic Region/Triode Region

Now by applying GATE voltage V GS transverse to the channel as shown in Figure 7.3.4 the channel thickness can be controlled and thereby the I-V slope can be controlled as shown in Figure 7.3.5.

In this OHMIC REGION of operation, we have two cases. First case is when V DS is kept less than 0.1V. In this case channel remains a parrallaelopied with a reduced thickness ‘t’. In this case if we continue to apply more and more negative voltage, the channel will be eventually be completed depleted and we say that the channel has pinched off. The negative gate voltage at which this occurs is known as Pinch-Off voltage (V P ).

There is a second case where V DS is greater than 0.1V and it continues to be increased. In this case the difference voltage between Gate and Drain>the difference between Gate and Source. Hence n-channel is trapezoidal and it does not give a linear I-V characteristics. This is also OHMIC REGION but non-linear. Linear and non-linear I-V curve is clearly indicated in Figure 7.3.5.

As seen in Figure 7.3.4 and Figure 7.3.5 we have achieved Voltage –Controlled Resistance (VCR) but this VCR is not quite linear. At V DS <0.1V, VCR is perfectly linear but at large V DS voltages the channel resistance deviates from the linear behavior.

In this kind of device at zero gate voltage, channel is present. Hence it is known as Normally-On . As the negative gate voltage is made more negative, the channel depletes until it finally completely pinches off . Hence it is known as .Depletion Type Device. As the gate voltage is made positive, channel becomes more conductive as it has a copious supply of electrons. Theefore we say that n-channel has enhanced.

Is there any normative that regulates the use of silver nanoparticles?
what king of growth are you checking .?
Renato
What fields keep nano created devices from performing or assimulating ? Magnetic fields ? Are do they assimilate ?
why we need to study biomolecules, molecular biology in nanotechnology?
?
Kyle
yes I'm doing my masters in nanotechnology, we are being studying all these domains as well..
why?
what school?
Kyle
biomolecules are e building blocks of every organics and inorganic materials.
Joe
anyone know any internet site where one can find nanotechnology papers?
research.net
kanaga
sciencedirect big data base
Ernesto
Introduction about quantum dots in nanotechnology
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absolutely yes
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for teaching engĺish at school how nano technology help us
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NANO
what is fullerene does it is used to make bukky balls
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s.
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Tarell
what is the actual application of fullerenes nowadays?
Damian
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is Bucky paper clear?
CYNTHIA
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so some one know about replacing silicon atom with phosphorous in semiconductors device?
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Harper
Do you know which machine is used to that process?
s.
how to fabricate graphene ink ?
for screen printed electrodes ?
SUYASH
What is lattice structure?
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Ebrahim
or in general
Ebrahim
in general
s.
Graphene has a hexagonal structure
tahir
On having this app for quite a bit time, Haven't realised there's a chat room in it.
Cied
what is biological synthesis of nanoparticles
how did you get the value of 2000N.What calculations are needed to arrive at it
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