Examcrazy Logo
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
Common Source Amplifier

Common Source Amplifier.
We’ve studied MOSFET small-signal equivalent models and the biasing of MOSFET amplifiers in the previous three lectures. We’ll now apply those skills by looking closely at three basic MOSFET amplifier types:
1. Common source amplifiers, including configurations with a source resistor (called source degeneration).
2. Common gate amplifiers.
3. Common drain (or source follower) amplifiers.
All of these amplifier types are appropriate for discrete component designs. In the case of IC amplifiers, we’ll also show corresponding designs implemented in CMOS, beginning in
Common Source Small-Signal Amplifier
This type of amplifier is shown in Fig. 4.43a, as biased by a combination of voltage and current sources:

Assuming sufficiently large values for the coupling capacitors (CC1 and CC2) and the bypass capacitor (CS) – so that their reactances are very small at the frequency of operation – the equivalent small-signal circuit for this amplifier is shown in

The text mentions performing the small-signal analysis directly on the amplifier circuit, as illustrated in Fig. 4.43(c). We do not recommend this approach. It is better to take the time and construct the small-signal equivalent circuit, as we’re doing here.
Small-Signal Amplifier Characteristics
As we did when studying BJT amplifiers, we’ll calculate the following quantities for this MOSFET common source amplifier: Rin, Av, Gv, Gi, and Rout.
• Input resistance, Rin. From the small-signal circuit above, and noting that ig =0 , then
Rin = R G
• Partial small-signal voltage gain, Av. From the output side of the small-signal circuit
V 0 = - GmV gs (r0||RD||RL)
while at the input,
V i=Vgs
Substituting (3) into (2), we find that the partial voltage gain as

• Overall small-signal voltage gain, Gv. As we did with BJT amplifiers, we can derive an expression for Gv in terms of Av. By definition,

Applying voltage division at the input of the small-signal equivalent circuit,

Substituting (6) into (5) and using (4) we find

• Overall small-signal current gain, Gi. Using current division at the output in the small-signal model above

while at the input,
Vgs= iiRG Substituting (9) into (8) we find that the overall small-signal current gain is

Notice that as RG ®¥ in this last expression, i G i® ¥. Is thisa problem? (To help answer this question, notice that as RG ®. ¥, ii® 0.) Also, what does Gi as RG ¥ mean for the overall small-signal output power of this amplifier?
• Output resistance, Rout. To calculate the output resistance, we first set vsig =0 , which also means that gm vgs =0 . The input impedance of the dependent current source is infinite. Consequently,
Rout= r0|| RD
In summary, we find for the CS small-signal amplifier that it has a
o High input resistance [see (1)].
o Relatively high small-signal voltage gain [see (7)].
o Very high small-signal current gain [see (10)].
o Relatively high output resistance [see (11)].

Discuss about DIODE here
Discussion Board for DIODE
You can discuss all your issues on DIODE here
Thread / Thread Starter Last Post Replies Views
Type of diode
I need short notes for all type of diode.

Posted By :-
Oct 27, 11:50:24 AM 0 11808
signals and system
hi i am venkatesh which author use in signal and system for gate

Posted By :-
Oct 13, 4:38:08 PM 0 11455
Thank u
i need some links to download free ebooks multiple choice for my gate preparation - V.Vivek Sharma.

Posted By :-
Oct 4, 9:56:42 AM 0 9082
study materials
i want to study materials of digital communication.

Posted By :-
Feb 6, 3:43:05 PM 4 23403
More examples of non linear circuit analysis
Notes are very simple to understand the concepts.

Posted By :-
Sep 9, 3:17:49 PM 0 15080
study materials
can i get some study materials by online

Posted By :-
Sep 4, 9:05:49 AM 0 11154
hiii plz give me basic information about electromegnetics
i have a dout between combination of electrostatics and megnetostatics

Posted By :-
Jul 29, 2:38:13 PM 0 9654
pls send me a link on answered problems on electronic devices and circuit theory by boylestad and nashelsky.. ty

Posted By :-
Jul 25, 11:21:28 PM 0 10771
electronics and communication
i am in 4th year

Posted By :-
Jun 10, 6:02:44 AM 0 9494
about bipolar device

Posted By :-
Feb 13, 2:11:36 PM 2 18331
h parameters of transister
i want h parameters of transister

Posted By :-
Feb 11, 7:52:45 AM 3 25456
very good tutorials
the explanations r very easy to understand

Posted By :-
Dec 7, 8:38:09 PM 0 9672
the explanation was nice...more of these explanations on other topics would be of much help and is expected urgently...

Posted By :-
Dec 2, 10:32:29 PM 0 10521
i want to simple way abt all the diode n jfet

Posted By :-
Jun 4, 10:25:28 AM 1 14328
Thanks for nice tutorials
Thanks for nice tutorials

Posted By :-
Nov 26, 8:29:06 AM 0 9912

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

(Members Login)

  About us | Privacy Policy | Terms and Conditions | Contact us | Email: support@Examcrazy.com  
Copyright © 2014 Extreme Testing House, India. All rights reserved.  8951