This chapter discusses small-signal modeling and linear amplification using transistors. The goals are to understand transistors as linear amplifiers, small-signal models, and amplifier characteristics. A simple common-emitter BJT amplifier circuit is presented and analyzed using DC and AC equivalent circuits. Key points include defining the Q-point, constructing small-signal models, and calculating voltage gain. Capacitor selection criteria are provided to maintain linearity in the amplifier.
I presented this slid in my last presentation about bipolar junction transistor configuration.Now I'm sharing this with all of you guys it can be helpful for you.
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The MOSFET is an important element in embedded system design which is used to control the loads as per the requirement. The MOSFET is a high voltage controlling device provides some key features for circuit designers in terms of their overall performance.
PN junction diode –structure, operation and V-I characteristics, diffusion and transient capacitance - Rectifiers – Half Wave and Full Wave Rectifier,– Display devices- LED, Laser diodes- Zener diodecharacteristics-Zener Reverse characteristics – Zener as regulator,TRANSISTORS, BJT, JFET, MOSFET- structure, operation, characteristics and Biasing UJT, Thyristor and IGBT Structure and characteristics,BJT small signal model – Analysis of CE, CB, CC amplifiers- Gain and frequency response –
MOSFET small signal model– Analysis of CS and Source follower – Gain and frequency response- High frequency analysis,BIMOS cascade amplifier, Differential amplifier – Common mode and Difference mode analysis – FET input stages – Single tuned amplifiers – Gain and frequency response – Neutralization methods, power amplifiers –Types (Qualitative analysis),Advantages of negative feedback – voltage / current, series , Shunt feedback –positive feedback – Condition for oscillations, phase shift – Wien bridge, Hartley, Colpitts and Crystal oscillators.
I presented this slid in my last presentation about bipolar junction transistor configuration.Now I'm sharing this with all of you guys it can be helpful for you.
Look at the beautiful view of forgiveness of mistakes.
Thank you
The MOSFET is an important element in embedded system design which is used to control the loads as per the requirement. The MOSFET is a high voltage controlling device provides some key features for circuit designers in terms of their overall performance.
PN junction diode –structure, operation and V-I characteristics, diffusion and transient capacitance - Rectifiers – Half Wave and Full Wave Rectifier,– Display devices- LED, Laser diodes- Zener diodecharacteristics-Zener Reverse characteristics – Zener as regulator,TRANSISTORS, BJT, JFET, MOSFET- structure, operation, characteristics and Biasing UJT, Thyristor and IGBT Structure and characteristics,BJT small signal model – Analysis of CE, CB, CC amplifiers- Gain and frequency response –
MOSFET small signal model– Analysis of CS and Source follower – Gain and frequency response- High frequency analysis,BIMOS cascade amplifier, Differential amplifier – Common mode and Difference mode analysis – FET input stages – Single tuned amplifiers – Gain and frequency response – Neutralization methods, power amplifiers –Types (Qualitative analysis),Advantages of negative feedback – voltage / current, series , Shunt feedback –positive feedback – Condition for oscillations, phase shift – Wien bridge, Hartley, Colpitts and Crystal oscillators.
Pre Final Year project/ mini project for Electronics and communication engine...Shirshendu Das
Mini project for Electronics and communication engineering (ECE) to build an AC to DC power supply using Full Wave Rectifier having input as 220-240V AC and giving stable filtered output of 5V, -5V & variable 5V DC. Simulation of the circuit was done in Proteus design suite.
EST 130, Transistor Biasing and Amplification.CKSunith1
The attached narrated power point presentation explains the need for biasing in transistor amplifiers and the different biasing arrangements used in transistor circuits. The material will be useful for KTU first year B Tech students who prepare for the subject EST 130, Part B, Basic Electronics Engineering.
A Bipolar Junction Transistor is a three-terminal semiconductor device consisting of two p-n junctions which are able to amplify or magnify a signal. It is a current controlled device. The three terminals of the BJT are the base, the collector and the emitter. A BJT is a type of transistor that uses both electrons and holes as charge carriers
Electrical current, voltage, resistance, capacitance, and inductance are a few of the basic elements of electronics and radio. Apart from current, voltage, resistance, capacitance, and inductance, there are many other interesting elements to electronic technology. ... Use Electronics Notes to learn electronics online.
TECHNICAL TRAINING MANUAL GENERAL FAMILIARIZATION COURSEDuvanRamosGarzon1
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Automobile Management System Project Report.pdfKamal Acharya
The proposed project is developed to manage the automobile in the automobile dealer company. The main module in this project is login, automobile management, customer management, sales, complaints and reports. The first module is the login. The automobile showroom owner should login to the project for usage. The username and password are verified and if it is correct, next form opens. If the username and password are not correct, it shows the error message.
When a customer search for a automobile, if the automobile is available, they will be taken to a page that shows the details of the automobile including automobile name, automobile ID, quantity, price etc. “Automobile Management System” is useful for maintaining automobiles, customers effectively and hence helps for establishing good relation between customer and automobile organization. It contains various customized modules for effectively maintaining automobiles and stock information accurately and safely.
When the automobile is sold to the customer, stock will be reduced automatically. When a new purchase is made, stock will be increased automatically. While selecting automobiles for sale, the proposed software will automatically check for total number of available stock of that particular item, if the total stock of that particular item is less than 5, software will notify the user to purchase the particular item.
Also when the user tries to sale items which are not in stock, the system will prompt the user that the stock is not enough. Customers of this system can search for a automobile; can purchase a automobile easily by selecting fast. On the other hand the stock of automobiles can be maintained perfectly by the automobile shop manager overcoming the drawbacks of existing system.
Sachpazis:Terzaghi Bearing Capacity Estimation in simple terms with Calculati...Dr.Costas Sachpazis
Terzaghi's soil bearing capacity theory, developed by Karl Terzaghi, is a fundamental principle in geotechnical engineering used to determine the bearing capacity of shallow foundations. This theory provides a method to calculate the ultimate bearing capacity of soil, which is the maximum load per unit area that the soil can support without undergoing shear failure. The Calculation HTML Code included.
Forklift Classes Overview by Intella PartsIntella Parts
Discover the different forklift classes and their specific applications. Learn how to choose the right forklift for your needs to ensure safety, efficiency, and compliance in your operations.
For more technical information, visit our website https://intellaparts.com
Cosmetic shop management system project report.pdfKamal Acharya
Buying new cosmetic products is difficult. It can even be scary for those who have sensitive skin and are prone to skin trouble. The information needed to alleviate this problem is on the back of each product, but it's thought to interpret those ingredient lists unless you have a background in chemistry.
Instead of buying and hoping for the best, we can use data science to help us predict which products may be good fits for us. It includes various function programs to do the above mentioned tasks.
Data file handling has been effectively used in the program.
The automated cosmetic shop management system should deal with the automation of general workflow and administration process of the shop. The main processes of the system focus on customer's request where the system is able to search the most appropriate products and deliver it to the customers. It should help the employees to quickly identify the list of cosmetic product that have reached the minimum quantity and also keep a track of expired date for each cosmetic product. It should help the employees to find the rack number in which the product is placed.It is also Faster and more efficient way.
Vaccine management system project report documentation..pdfKamal Acharya
The Division of Vaccine and Immunization is facing increasing difficulty monitoring vaccines and other commodities distribution once they have been distributed from the national stores. With the introduction of new vaccines, more challenges have been anticipated with this additions posing serious threat to the already over strained vaccine supply chain system in Kenya.
Student information management system project report ii.pdfKamal Acharya
Our project explains about the student management. This project mainly explains the various actions related to student details. This project shows some ease in adding, editing and deleting the student details. It also provides a less time consuming process for viewing, adding, editing and deleting the marks of the students.
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Event Management System Vb Net Project Report.pdfKamal Acharya
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2. Chapter Goals
Understanding of concepts related to:
• Transistors as linear amplifiers
• dc and ac equivalent circuits
• Use of coupling and bypass capacitors to modify dc and ac equivalent
circuits
• Small-signal voltages and currents
• Small-signal models for diodes and transistors
• Identification of common-emitter amplifiers
• Amplifier characteristics such as voltage gain, input and output
resistances and linear signal range
• Rule-of-thumb estimates for voltage gain of common-emitter
amplifiers.
3. Introduction to Amplifiers
• The BJT is an an excellent amplifier when biased in the forward-active
region.
• The FET can be used as an amplifier if operated in the saturation
region.
• In these regions, the transistors can provide high voltage, current and
power gains.
• DC bias is provided to stabilize the operating point in the desired
operation region.
• The DC Q-point also determines
– The small-signal parameters of the transistor
– The voltage gain, input resistance, and output resistance
– The maximum input and output signal amplitudes
– The overall power consumption of the amplifier
4. A Simple BJT Amplifier
The BJT is biased in the forward active region by dc voltage sources VBE
and VCC = 10 V. The DC Q-point is set at, (VCE, IC) = (5 V, 1.5 mA) with IB
= 15 µA.
Total base-emitter voltage is: be
v
BE
V
BE
v +=
Collector-emitter voltage is: This produces a load line.C
R
C
i
CE
v −=10
5. BJT Amplifier (continued)
An 8 mV peak change in vBE gives a 5
µA change in iB and a 0.5 mA change
in iC.
The 0.5 mA change in iC gives a 1.65
V change in vCE .
If changes in operating currents and
voltages are small enough, then IC
and VCE waveforms are undistorted
replicas of the input signal.
A small voltage change at the base
causes a large voltage change at the
collector. The voltage gain is given
by:
The minus sign indicates a 1800
phase shift between input and
output signals.
˜Av =
˜vce
˜v
be
=
1.65∠180
0.008∠0
=206∠180=−206
6. A Simple MOSFET Amplifier
The MOSFET is biased in the saturation region by dc voltage sources VGS and
VDS = 10 V. The DC Q-point is set at (VDS, IDS) = (4.8 V, 1.56 mA) with VGS =
3.5 V.
Total gate-source voltage is: gsv
GS
V
GS
v +=
A 1 V p-p change in vGS gives a 1.25 mA p-p change in iDS and a 4 V p-p change
in vDS. Notice the characteristic non-linear I/O relationship compared to the BJT.
7. A Practical BJT Amplifier using
Coupling and Bypass Capacitors
• AC coupling through capacitors is
used to inject an ac input signal and
extract the ac output signal without
disturbing the DC Q-point
• Capacitors provide negligible
impedance at frequencies of interest
and provide open circuits at dc.
In a practical amplifier design, C1 and
C3 are large coupling capacitors or dc
blocking capacitors, their reactance (XC
= |ZC| = 1/ωC) at signal frequency is
negligible. They are effective open
circuits for the circuit when DC bias is
considered.
C2 is a bypass capacitor. It provides a
low impedance path for ac current from
emitter to ground. It effectively
removes RE (required for good Q-point
stability) from the circuit when ac
signals are considered.
8. DC and AC Analysis -- Application of
Superposition
• DC analysis:
– Find the DC equivalent circuit by replacing all capacitors by open
circuits and inductors (if any) by short circuits.
– Find the DC Q-point from the equivalent circuit by using the
appropriate large-signal transistor model.
• AC analysis:
– Find the AC equivalent circuit by replacing all capacitors by short
circuits, inductors (if any) by open circuits, dc voltage sources by
ground connections and dc current sources by open circuits.
– Replace the transistor by its small-signal model (to be developed).
– Use this equivalent circuit to analyze the AC characteristics of the
amplifier.
– Combine the results of dc and ac analysis (superposition) to yield the
total voltages and currents in the circuit.
9. DC Equivalent for the BJT Amplifier
• All capacitors in the original amplifier circuit are replaced by open
circuits, disconnecting vI, RI, and R3 from the circuit and leaving RE
intact. The the transistor Q will be replaced by its DC model.
DC Equivalent Circuit
10. AC Equivalent for the BJT Amplifier
• The coupling and bypass capacitors are replaced by short circuits. The DC
voltage supplies are replaced with short circuits, which in this case connect
to ground.
11. AC Equivalent for the BJT Amplifier
(continued)
R
B
=R
1
R
2
=10kΩ30kΩ
R=R
C
R
3
=4.3kΩ100kΩ
• By combining parallel resistors into equivalent RB and R, the equivalent AC
circuit above is constructed. Here, the transistor will be replaced by its
equivalent small-signal AC model (to be developed).
12. Hybrid-Pi Small-signal AC Model for
the BJT
• The hybrid-pi small-signal
model is the intrinsic low-
frequency representation of the
BJT.
• The small-signal parameters are
controlled by the Q-point and
are independent of the geometry
of the BJT.
Transconductance:
gm =
I
C
V
T
≅40I
C
Input resistance:
rπ=
βoV
T
I
C
=
βo
gm
Output resistance:
ro=
V
A
+V
CE
I
C
13. Small-signal Current Gain and
Amplification Factor of the BJT
−
∂
∂
−
==
int
1
1
poQC
i
F
F
C
I
Frmgo
β
β
β
πβ
βo > βF for iC < IM, and βo < βF for
iC > IM, however, βo and βF are
usually assumed to be about
equal.
The amplification factor is given by:
For VCE << VA,
µF represents the maximum voltage
gain an individual BJT can provide,
independent of the operating point.
µ
F
≅
V
A
V
T
≅40V
A
µF ≡
vce
vbe
,vce =−rogmvbe
µ
F
=gmro=
I
C
V
T
V
A
+V
CE
I
C
=
V
A
+V
CE
V
T
14. Example βo Calculation for 2N2222A
Choose the Q-point at about (5 V, 5 mA) for this analysis. Notice the slope of
the DC current gain characteristic in this region. Ideally, the slope would be
zero.
16. Equivalent Forms of the Small-signal
Model for the BJT
• The voltage-controlled current source gmvbe can be transformed into a
current-controlled current source,
• The basic relationship ic=βib is useful in both dc and ac analysis when
the BJT is biased in the forward-active region.
v
be
=i
b
rπ =i
b
βo
gm
∴gmv
be
=gmi
b
rπ =βoi
b
ic =gmv
be
+
vce
ro
≅gmv
be
=βoi
b
17. Small Signal Operation of BJT
++++=
=+=∴
...
3
6
1
2
2
11
expexp
T
V
be
v
T
V
be
v
T
V
be
v
C
I
T
V
be
v
T
V
BE
V
S
Ici
C
I
C
i
=
T
V
BE
v
S
I
C
i exp
+++=−=∴ ...
3
6
1
2
2
1
T
V
be
v
T
V
be
v
T
V
be
v
C
I
C
I
C
ici
For linearity, ic should be directly proportional to vbe.
v
be
<<2V
T
=50 mV∴ic ≅I
C
v
be
V
T
=
I
C
V
T
v
be
=gmv
be
If we limit vbe to 5 mV, the relative change in ic compared to IC that
corresponds to small-signal operation is:
ic
I
C
=
gmv
be
I
C
=
v
be
V
T
≤
0.005
0.025
=0.200
for
18. Small-Signal Analysis of the Complete
C-E Amplifier: AC Equivalent
• The AC equivalent circuit is
constructed by assuming that all
capacitances have zero
impedance at signal frequency
and the AC voltage source is at
ground.
• Assume that the DC Q-point has
already been calculated.
19. Small-Signal Analysis of Complete C-E
Amplifier: Small-Signal Equivalent
R
L
=ro R
C
R
3
Overall voltage gain from source vi
to output voltage vo across R3 is:
Av =
vo
v
i
=
vo
v
be
v
be
v
i
∴Av =−gmR
L
R
B
rπ
R
I
+ R
B
rπ( )
vo=−gmv
be
R
L
and
v
be
=
v
i
R
B
rπ
R
I
+ R
B
rπ
20.
21. Capacitor Selection for the CE Amplifier
Zc =
1
jωC
Capacitive Reactance Xc ≡Zc =
1
ωC
where ω=2πf
X
c1
<<R
B
rπ∴Make X
c1
≤0.01 R
B
rπ
for < 1% gain error.
X
c2
⇒0 ∴Make X
c2
≤1Ωfor <1% gain error.
X
c3
<<R
3
∴Make X
c3
≤0.01 R
3
for <1% gain error.
The key objective in design is to make the capacitive reactance
much smaller at the operating frequency f than the associated
resistance that must be coupled or bypassed.
22.
23. C-E Amplifier Input Resistance
• The input resistance, the total
resistance looking into the
amplifier at coupling capacitor C1,
represents the total resistance
presented to the AC source.
ππ
π
rRRr
B
RR
r
B
R
21
xi
xv
in
)(xixv
===
=
24. C-E Amplifier Output Resistance
• The output resistance is the total
equivalent resistance looking into the
output of the amplifier at coupling
capacitor C3. The input source is set to 0
and a test source is applied at the output.
C
Ror
C
RR
mg
or
C
R
≅==∴
++=
xi
xv
out
be
vxvxv
xi But vbe=0.
since ro is usually >> RC.
30. Amplifier Power Dissipation
• Static power dissipation in amplifiers is determined from their DC
equivalent circuits.
P
D
=V
CE
I
C
+V
BE
I
B
Total power dissipated in C-B
and E-B junctions is:
where
Total power supplied is:
P
S
=V
CC
I
C
+I
2
where I
2
=I
1
+I
B
BE
V
CB
V
CE
V +=
I
1
=
V
CC
R
1
+R
2
and I
B
=
V
EQ
−V
BE
R
EQ
+β
F
+1
R
E
The difference is the power dissipated by the bias resistors.