Examcrazy Logo
HOME  SITEMAP CONTACT US LOGIN
HOME Engineering AIEEE GATE IES DRDO-SET BSNL-JTO
MBA in India CAT How to Prepare for Exams Technical Freshers Jobs
  Follow us|  twitter  Orkut  facebook
MOSFET Tutorials
   Enhancement Type MOSFET Operation, P-Channel, and CMOS
   MOSFET Circuit Symbols, iD-vDS Characteristics
   MOSFET as an Amplifier. Small-Signal Equivalent Circuit Models
   MOSFET Small-Signal Amplifier Examples
   Biasing MOSFET Amplifiers. MOSFET Current Mirrors
   Biasing MOSFET Amplifiers. MOSFET Current Mirrors
   Common Source Amplifier
   Common Source Amplifier with Source Degeneration.
   CMOS Common Source Amplifier
   MOSFET Common Gate Amplifier
   CMOS Common Gate Amplifier
Free Electronics Tutorials
   Diode Tutorials
   BJT Tutorials
   MOSFET Tutorials
   Electronics II Tutorials
   Applied Electromagnetics Tutorials
   Microwave Tutorials
GATE preparation tips
   GATE Books & How to prepare
   Objective Solving Tricks
   Other GATE links
   IES exam preparation
   All about DRDO-SET
More Engineering Links
   Directory of coaching Institutes
   Govt engg college rankings
   Private engg college rankings
   Admission notifications for Mtech/PhD
   All Engineering Colleges in India
MOSFET Circuit Symbols

MOSFET Circuit Symbols,
iD-vDS Characteristics.
There are two circuit symbols you may encounter for the enhancement type MOSFET. For the n-channel, one symbol is

Referring to this circuit symbol:
The arrowed terminal indicates the source,
This arrow direction indicates n-type (direction of current)
The gap at the gate indicates the oxide layer.
However, the body is often connected to the source. This leads to a more common circuit symbol:

Similar circuit symbols are used for p-channel enhancement type
MOSFETS:

MOSFET iD–vDS Characteristics
Similar to a BJT, we can generate a set of iD–vDS characteristic curves for a MOSFET by setting vGS and varying vDS. This is shown in Fig. 4.11 for an n-type MOSFET:

There are three regions of operation:
(1) Cutoff. To operate an enhancement type MOSFET, we first must induce the channel. For NMOS, this means that vGD= Vt (induce) If vGS < Vt there is no channel and the device is cutoff, which we see in When the MOSFET is cutoff, iD = iS = 0.
2) Triode. To operate in this mode, we first must induce the channel as in (1) above. We must also keep vDS small enough so the channel is continuous (not pinched off): VGD >Vt
[Note how similar this last criterion is to VGD >Vt for the channel to be induced. Here in (2), we have VGD >Vt for a continuous channel at the drain end. This observation can help us to remember these criterion.] Another way of writing this criterion in (2) is in terms of vDS. Referring to this circuit element

we see that
VDS=VGS+VDG
For a continuous channel, as required by (2), (3) becomesv
VDs-VGS=VDG<-Vt
Therefore,
VDSGS-Vt(continuous)
We can use either (2) or (4) to check for triode operation of the MOSFET. As given in the last lecture, in the triode region
.
where rDS is defined as the (linear) resistance between the drain and source terminals. The value of rDS is controlled by vGS.
(3) Saturation. To operate in this mode we need to first induce the channel
VGS³ Vt(pinch off)
then ensure that the channel is pinched off at the drain end
VGS³ Vt(pinch off)
or equivalently
VGS³VGS(inch off)
As we saw in the previous lecture, the drain current in this region is

and is not dependent on vDS. A plot of iD versus vGS for an enhancement type NMOS device in saturation is shown in

In the saturation mode, this device behaves as an ideal current source controlled by vGS:

In reality, though, there is a finite output resistance (ro) that should be added to this model:

where

This finite output resistance gives a slope to the iD–vDS characteristic curves:

Example N26.1 (similar to text exercise 4.4). Given an enhancement type NMOS with Vt = 2 V.

Determine the region of operation of this device for the following VD. Use these criteria for the region of operation:
Cutoff: VGS>Vt
Triode: V GS³ V t and V DSGS-Vt
Saturation : VGS³ Vtand VDS³ VGS-Vt

Example N26.2 (similar to text problem 4.16). An NMOS enhancement type MOSFET has Vt = 2 V. If VGS ranges from 2.5 to 5 V what is the largest VDS for which the channel remains continuous?

V GS > V t, V GS . so the channel is always present. Then for the channel to remain open at the drain end, V DS< V GS - V t (triode) Which VGS to use here? The smallest. Therefore, V DS| max < 2.5-2= 0.5 V


Discuss about MOSFET here
   START NEW THREADS
Discussion Board for MOSFET
You can discuss all your issues on MOSFET here
Thread / Thread Starter Last Post Replies Views
fourier transform
sir,
plz send me the notes for fourier transforms its very urgent.


Posted By :-
 shruthi.s
Aug 31, 12:14:03 PM 0 54557
Fourier Transform
Sir I want tutorial on Fourier Transform.........


Posted By :-
 jainpooja.1989@yahoo.com
Jul 15, 3:24:49 PM 0 57555
fourier transform
sir i want tutorial on fourier transform


Posted By :-
 apseng2005
Jul 11, 10:08:19 AM 0 53928
match filter
heloo sir ,i want a tutorial for match filter.plz send it as soon as possible it is very urgent.


Posted By :-
 richa
Jun 4, 2:25:18 AM 0 74873
Electic circuits
I want lecture notes for single phase ac & 3phase ac circuits


Posted By :-
 kalaivanisudhagar
May 21, 11:32:46 AM 1 90863
electro statics
what is the work done to move a charge? derive an expression for assembling a configuration of point charges


Posted By :-
 harismhkt
May 12, 8:28:18 AM 0 53301
electromagnetic waves
i want lcr circiut teorems derivations


Posted By :-
 harismhkt
May 12, 8:23:58 AM 0 52897
oscillators
i want oscillator frequency derivations for all. plz let me know from where i can get that


Posted By :-
 shruthi.s
May 4, 5:21:01 PM 0 53800
Equivalent circuit Models
I've got a question in one of my revision papers,

Explain the advantages of representing a transistor by means of an equivalent circuit circuit model

The only thing i can remember is that you can take complex circuits and break them down into simpler circuits which are easier to understand,

Is this the only advantage or do you have any more?

Please help!


Posted By :-
 ally79
Apr 12, 6:33:57 PM 2 114176
temperature Vs reverse satuation current
I want to know the variation of reverse saturation current with the increase in temperature for both germanium and silicon diodes


Posted By :-
 bhrahma@yahoo.co.in
Jan 28, 7:17:23 PM 0 59914
communication system
analog and digital communication system, fiber optic communication, telecommunication technique and application, mobile communication


Posted By :-
 hirakec@gmail.com
Dec 17, 10:38:27 AM 0 66184
CMOS TRANSISTOR
I WANT A TUTORIAL FOR CMOS TRANSISTORS.


Posted By :-
 maroofalamkhan
Dec 14, 3:29:22 PM 0 65455
coaching in ies in indore
what about coaching


Posted By :-
 satish21
Dec 7, 5:27:52 PM 0 69922

To start your new thread you must login here.
New user signup at ExamCrazy.com Exam Crazy
To reply/post a comment you need to login, Use your user name and password to login if you are already registered else register here

EXISTING USER LOGIN
(Members Login)
Username:
Password:
NEW USER REGISTERATION FORM
Login-Id
Email-ID
Password
Confirm-Password
Full-Name

  About us | Privacy Policy | Terms and Conditions | Contact us | Email: support@Examcrazy.com  
Copyright © 2014 Extreme Testing House, India. All rights reserved.  159487