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SSPD_Chapter 7_Part 6_Basic Circuit Concepts_continued2 calculates the charging time constant of the Gate of NMOS through a Pass Transistor.

SSPD_Chapter 7_Part 6_Basic Circuit Concepts_continued2

7.6.3. Charging and discharging delay in CMOS.

Like all the Logic Gates, MOS Logic also experiences propogation delay which results in the degradation of the toggle rate og CMOS gates. In order to minimize this degradation it is important to quantitatively analyze the propogatioon delay.

In Figure 7.6.3.1. we have a NMOS being driven through a NMOS Pass Transistor by V DD magnitude Step Voltage where V DD has a magnitude of 5V.

As seen in the Figure 7.6.3.1, a 5V step input results in exponentially growing Gate Voltage. With a time-dealay of τ = RC , Gate Voltage rises to 0.63×5V. This is evident from the charging equation given in the diagram.

Here R = resistance of the n-channel of pass transistor under ON condition

=Sheet Resistance of the channel×(L channel /W channel )=R channel ;

From Table 4.6.1, for 5μm Generation Technology R sheet of n-channel = 10 4 Ω/□ and

L channel = 2λ and W channel = 2λ.

Therefore R chanel = 10kΩ×(2λ/2λ)= 10kΩ;

C = gate-to-channel area capacitance = C g = area of the gate×□C gate-to-channel =0.01pF from the Table 7.6.3 for 5μm Generation.

Hence

For 5μm Generation charging time constant = R chanel × C g = 10kΩ×0.01pF =τ = 0.1nsec;

For 2μm Generation charging time constant = R chanel × C g = 20kΩ×0.0032pF

=τ = 0.064nsec;

For 1.2μm Generation charging time constant = R chanel × C g = 20kΩ×0.0023pF

=τ = 0.046nsec;

In Table 7.6.3.1 these delays for different generations are tabulated.

Table 7.6.3.1. Delay Time Calculation for 5μm, 2μm and 1.2μm Generations.

Generation R channel C gate τ charging τ transit
5μm 10kΩ 0.01pF 0.1nsec 0.13nsec
2μm 20kΩ 0.0032pF 0.064sec 0.04nsec
1.2μm 20kΩ 0.0023pF 0.046nsec 0.03nsec

In Basic Electrical Properties Chapter 7.3, Equation 7.3.7, the transit time through the channel is given by the equation:

Where L = 5/2/1.2μm, μ n = 650cm 2 /(V-sec), V ds = average of V DD = 3V/1.5V/0.75V

By taking the values of the parameters in Equation 7.3.7 we arrive at the transit time tabulated in Table 7.6.3.1.

By inspection of Table 7.6.3.1 we find that with scaling the charging delay decreases and speed performance correspondingly improves.

Since time constant of charging and transit time are nearly equal they are interchangeably used and it is also used as the fundamentl time unit. All timings in a system can be assessed in terms of charging time constant.

To account the variation in the parameters of the devices, we always take the worst case scenario namely 0.3nsec for 5μm Generation, 0.2nsec for 2μm Generation and 0.1nsec for 1.2μm Generation.

We conclude that standard delay unit = τ = R (sheet resiatance of the n-channel)×□C g ;

Questions & Answers

where we get a research paper on Nano chemistry....?
Maira Reply
nanopartical of organic/inorganic / physical chemistry , pdf / thesis / review
Ali
what are the products of Nano chemistry?
Maira Reply
There are lots of products of nano chemistry... Like nano coatings.....carbon fiber.. And lots of others..
learn
Even nanotechnology is pretty much all about chemistry... Its the chemistry on quantum or atomic level
learn
Google
da
no nanotechnology is also a part of physics and maths it requires angle formulas and some pressure regarding concepts
Bhagvanji
hey
Giriraj
Preparation and Applications of Nanomaterial for Drug Delivery
Hafiz Reply
revolt
da
Application of nanotechnology in medicine
what is variations in raman spectra for nanomaterials
Jyoti Reply
ya I also want to know the raman spectra
Bhagvanji
I only see partial conversation and what's the question here!
Crow Reply
what about nanotechnology for water purification
RAW Reply
please someone correct me if I'm wrong but I think one can use nanoparticles, specially silver nanoparticles for water treatment.
Damian
yes that's correct
Professor
I think
Professor
Nasa has use it in the 60's, copper as water purification in the moon travel.
Alexandre
nanocopper obvius
Alexandre
what is the stm
Brian Reply
is there industrial application of fullrenes. What is the method to prepare fullrene on large scale.?
Rafiq
industrial application...? mmm I think on the medical side as drug carrier, but you should go deeper on your research, I may be wrong
Damian
How we are making nano material?
LITNING Reply
what is a peer
LITNING Reply
What is meant by 'nano scale'?
LITNING Reply
What is STMs full form?
LITNING
scanning tunneling microscope
Sahil
how nano science is used for hydrophobicity
Santosh
Do u think that Graphene and Fullrene fiber can be used to make Air Plane body structure the lightest and strongest. Rafiq
Rafiq
what is differents between GO and RGO?
Mahi
what is simplest way to understand the applications of nano robots used to detect the cancer affected cell of human body.? How this robot is carried to required site of body cell.? what will be the carrier material and how can be detected that correct delivery of drug is done Rafiq
Rafiq
if virus is killing to make ARTIFICIAL DNA OF GRAPHENE FOR KILLED THE VIRUS .THIS IS OUR ASSUMPTION
Anam
analytical skills graphene is prepared to kill any type viruses .
Anam
Any one who tell me about Preparation and application of Nanomaterial for drug Delivery
Hafiz
what is Nano technology ?
Bob Reply
write examples of Nano molecule?
Bob
The nanotechnology is as new science, to scale nanometric
brayan
nanotechnology is the study, desing, synthesis, manipulation and application of materials and functional systems through control of matter at nanoscale
Damian
Is there any normative that regulates the use of silver nanoparticles?
Damian Reply
what king of growth are you checking .?
Renato
What fields keep nano created devices from performing or assimulating ? Magnetic fields ? Are do they assimilate ?
Stoney Reply
why we need to study biomolecules, molecular biology in nanotechnology?
Adin Reply
?
Kyle
yes I'm doing my masters in nanotechnology, we are being studying all these domains as well..
Adin
why?
Adin
what school?
Kyle
biomolecules are e building blocks of every organics and inorganic materials.
Joe
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Source:  OpenStax, Solid state physics and devices-the harbinger of third wave of civilization. OpenStax CNX. Sep 15, 2014 Download for free at http://legacy.cnx.org/content/col11170/1.89
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