section 5.6 small signal model & analysis. quiz no 1 de 27 (ce) state the purpose and four steps...
TRANSCRIPT
![Page 1: Section 5.6 Small Signal Model & Analysis. Quiz No 1 DE 27 (CE) State the purpose and four steps (each) that are to be taken for carrying out (a)DC Analysis](https://reader038.vdocuments.mx/reader038/viewer/2022102415/56649ec15503460f94bcd8fc/html5/thumbnails/1.jpg)
Section 5.6
Small Signal Model & Analysis
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Quiz No 1 DE 27 (CE)
State the purpose and four steps (each) that are to be taken for carrying out
(a)DC Analysis
(b) Small signal Analysis
06-03-07
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The operation of the transistor as an amplifier.
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Conceptual circuit with the signal source eliminated .
(vbe =0)
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DC Analysis Signal source eliminated
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The collector Current & Trans-conductance
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The collector Current & Trans-conductance
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Output resistance is infinity
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Linear operation of the transistor under the small-signal condition:
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Base Current & Input Resistance at the Base
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Emitter Current & Input Resistance @ Emitter
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Voltage Gain
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DC-AC Models
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Large Signal Model Small Signal Model
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The amplifier circuit
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Figure 5.51 Two slightly different versions of the simplified hybrid- model for the small-signal operation of the BJT.
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Figure 5.52 Two slightly different versions of what is known as the T model of the BJT.
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Small Signal Analysis
• Coupling Capacitors– Couples the input signal vi to the emitter while
blocks the DC signals
– Don’t let dc biasing established by VCC &VEE be disturbed. when vi is connected
– Capacitor is of very large value –infinite, acts as short circuit at signal frequency of interest.
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Application (Steps) : Small Signal Model• Suppress ac independent sources
– ac Voltage Sources be short circuited– ac Current Sources be open circuited– Capacitors be Open circuited
• Determine DC operating Point IC
• Suppress DC independent sources – DC Voltage Sources be short circuited– DC Current Sources be open circuited– Capacitors be short circuited
• Replace BJT with small signal Model
• Analyze the resulting circuit of find voltage gain & input/output resistance
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Small Signal Analysis
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The Early Effect
• In real world
– (a) Collector current does show some dependence on collector voltage
– (b) Characteristics are not perfectly horizontal line
CEC vi
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Figure 5.19 (a) Conceptual circuit for measuring the iC –vCE characteristics of the BJT. (b) The iC –vCE characteristics of a practical BJT.
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Figure 5.58 The hybrid-pi small-signal model, in its two versions, with the resistance ro included.
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Problem 5.130
• Find the common-emitter amplifier shown in Fig. P5.130, Let VCC =9V, R1 = 27kΩ, R2 = 15kΩ, RE = 1.2kΩ, and Rc = 2.2kΩ. The transistor has β = 100 and VA = 100 V. Calculate the dc bias current IE. If the amplifier operates between a source for which Rsig = 10 kΩ and a load of 2kΩ replace the transistor with its hybrid-Π model, and find the value of Rm, the voltage gain and the current gain i
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Figure P5.130
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Figure P5.130
DC Analysis
Suppress the AC (independent Sources)Short Circuit Voltage Sources
Open Circuit the Capacitors
Calculate DC Node Voltages & Loop Currents
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Figure P5.130
DC Analysis
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Solution P5.130
• DC Values
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1.92 mA
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• Check for Mode
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Solution P5.130
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• Small Signal Model
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Solution P5.130sigv
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CE with pi Model
![Page 33: Section 5.6 Small Signal Model & Analysis. Quiz No 1 DE 27 (CE) State the purpose and four steps (each) that are to be taken for carrying out (a)DC Analysis](https://reader038.vdocuments.mx/reader038/viewer/2022102415/56649ec15503460f94bcd8fc/html5/thumbnails/33.jpg)
CE with ‘T’ Model
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Comparison ‘pi’ Vs ‘T’ Model
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Single Stage BJT Amplifier
• Three Configurations
– Common Emitter (CE)• Common Emitter (CE) with Emitter Resistance
– Common Base (CB)– Common Collector (CC)
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Figure 5.60 (a) A common-emitter amplifier using the structure of Fig. 5.59.
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Amplifiers Configurations
Common Emitter
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Amplifiers Configurations Common Emitter
DC AnalysisSuppress Independent ac Source Voltage source ----- Short Cct Current Sources --- Open
Capacitors ---- Open Cct
Redraw the Circuit
Analysis
IE=IIC=αIE
IB=(β+1)IE
VC=VCC-ICRC
VB=-IBRB
VE=VB-VBE
VC
VE
VB
gm=Ic/VT
rл=β/gm
re=α/gm
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Amplifiers Configurations Common Emitter
Small Signal AnalysisSuppress Independent DC Source Voltage source ----- Short Cct Current Sources --- Open
Capacitors ---- Short Cct
Redraw the Circuit by replacing BJTWith pi Model
Analysisgm=Ic/VT
rл=β/gm
re=α/gm
Find Rin, Rout, Voltage Gain vo/vi
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Common Emitter
Rin=RB||rл
Rout=RC|RL
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Ais=-gmRin
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Summary : CE rrRR Bi ~||
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Input Resistance
Output Resistance
Open Circuit Voltage Gain
Short Circuit Current Gain
Low to moderate typically a few kilohms
Voltage gain of a few hundred
Current gain equal to β
Output Resistance is relatively low
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Figure 5.61 (a) A common-emitter amplifier with an emitter resistance Re.
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Quiz No 2 (DE 27 CE)
Redraw the circuit for DC analysis Redraw the circuit for Small Signal pi model analysis
13-03-2007
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Figure 5.61 (a) A common-emitter amplifier with an emitter resistance Re.
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Figure 5.61 (a) A common-emitter amplifier with an emitter resistance Re.
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Small Signal Analysis : CE with Emitter ResistanceInput Resistance
Multiplication by a factor (1+β) is known as the Resistance Reflection Rule.
Analysis
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Small Signal Analysis : CE with Emitter ResistanceVoltage Gain
Voltage gain is lower than that of CE because of the additional term (1+β)Re
![Page 50: Section 5.6 Small Signal Model & Analysis. Quiz No 1 DE 27 (CE) State the purpose and four steps (each) that are to be taken for carrying out (a)DC Analysis](https://reader038.vdocuments.mx/reader038/viewer/2022102415/56649ec15503460f94bcd8fc/html5/thumbnails/50.jpg)
Small Signal Analysis : CE with Emitter ResistanceCurrent Gain
![Page 51: Section 5.6 Small Signal Model & Analysis. Quiz No 1 DE 27 (CE) State the purpose and four steps (each) that are to be taken for carrying out (a)DC Analysis](https://reader038.vdocuments.mx/reader038/viewer/2022102415/56649ec15503460f94bcd8fc/html5/thumbnails/51.jpg)
Small Signal Analysis : CE with Emitter Resistance
Summary
Re introduces negative feedback gives it the name emitter degenerative resistance
![Page 52: Section 5.6 Small Signal Model & Analysis. Quiz No 1 DE 27 (CE) State the purpose and four steps (each) that are to be taken for carrying out (a)DC Analysis](https://reader038.vdocuments.mx/reader038/viewer/2022102415/56649ec15503460f94bcd8fc/html5/thumbnails/52.jpg)
Comparison ‘T’ Vs ‘pi’ Model
![Page 53: Section 5.6 Small Signal Model & Analysis. Quiz No 1 DE 27 (CE) State the purpose and four steps (each) that are to be taken for carrying out (a)DC Analysis](https://reader038.vdocuments.mx/reader038/viewer/2022102415/56649ec15503460f94bcd8fc/html5/thumbnails/53.jpg)
A common-base amplifier
![Page 54: Section 5.6 Small Signal Model & Analysis. Quiz No 1 DE 27 (CE) State the purpose and four steps (each) that are to be taken for carrying out (a)DC Analysis](https://reader038.vdocuments.mx/reader038/viewer/2022102415/56649ec15503460f94bcd8fc/html5/thumbnails/54.jpg)
A common-base amplifier with its T model.
![Page 55: Section 5.6 Small Signal Model & Analysis. Quiz No 1 DE 27 (CE) State the purpose and four steps (each) that are to be taken for carrying out (a)DC Analysis](https://reader038.vdocuments.mx/reader038/viewer/2022102415/56649ec15503460f94bcd8fc/html5/thumbnails/55.jpg)
CB has low input resistance
CB is non-inverting amplifier
Small Signal Analysis : CB
![Page 56: Section 5.6 Small Signal Model & Analysis. Quiz No 1 DE 27 (CE) State the purpose and four steps (each) that are to be taken for carrying out (a)DC Analysis](https://reader038.vdocuments.mx/reader038/viewer/2022102415/56649ec15503460f94bcd8fc/html5/thumbnails/56.jpg)
• Very Low input resistance
Rin=re
• Short Circuit Current Gain is nearly unity
• Open circuit Voltage Gain is equal to CE and is positive
gm RC
• Relatively high output resistance (Rc) same as CE
• Excellent high frequency performance
• As short circuit current gain is unity Current Buffer, it accept an input signal current at a low input resistance and delivers equal current at a very high output resistance.
Summary : CB
![Page 57: Section 5.6 Small Signal Model & Analysis. Quiz No 1 DE 27 (CE) State the purpose and four steps (each) that are to be taken for carrying out (a)DC Analysis](https://reader038.vdocuments.mx/reader038/viewer/2022102415/56649ec15503460f94bcd8fc/html5/thumbnails/57.jpg)
An emitter-follower circuit : Common Collector
Non-unilateral Amplifier Input Resistance depends upon RL
Output Resistance depends upon Rsig
![Page 58: Section 5.6 Small Signal Model & Analysis. Quiz No 1 DE 27 (CE) State the purpose and four steps (each) that are to be taken for carrying out (a)DC Analysis](https://reader038.vdocuments.mx/reader038/viewer/2022102415/56649ec15503460f94bcd8fc/html5/thumbnails/58.jpg)
Common Collector An emitter-follower circuit : T model
![Page 59: Section 5.6 Small Signal Model & Analysis. Quiz No 1 DE 27 (CE) State the purpose and four steps (each) that are to be taken for carrying out (a)DC Analysis](https://reader038.vdocuments.mx/reader038/viewer/2022102415/56649ec15503460f94bcd8fc/html5/thumbnails/59.jpg)
An equivalent circuit of the Emitter Follower - CC
![Page 60: Section 5.6 Small Signal Model & Analysis. Quiz No 1 DE 27 (CE) State the purpose and four steps (each) that are to be taken for carrying out (a)DC Analysis](https://reader038.vdocuments.mx/reader038/viewer/2022102415/56649ec15503460f94bcd8fc/html5/thumbnails/60.jpg)
An equivalent circuit of the Emitter Follower - CC
Overall Voltage Gain is less than unity:RB>>Rsig, (β+1)(re+(ro||RL))>>(Rsig||RL)
The voltage at the emitter (vo) follows very closely the voltage at the input thus give the circuit the name Emitter Follower
![Page 61: Section 5.6 Small Signal Model & Analysis. Quiz No 1 DE 27 (CE) State the purpose and four steps (each) that are to be taken for carrying out (a)DC Analysis](https://reader038.vdocuments.mx/reader038/viewer/2022102415/56649ec15503460f94bcd8fc/html5/thumbnails/61.jpg)
The emitter follower : Reflecting resistance into emitter
For RB>> Rsig & ro >> RL Gain approaches Unity when Rsig/(1+β)<<RL89
Short Circuit Current Gain = 1+β
![Page 62: Section 5.6 Small Signal Model & Analysis. Quiz No 1 DE 27 (CE) State the purpose and four steps (each) that are to be taken for carrying out (a)DC Analysis](https://reader038.vdocuments.mx/reader038/viewer/2022102415/56649ec15503460f94bcd8fc/html5/thumbnails/62.jpg)
Common Collector : Output Resistance
Output Resistance is low
![Page 63: Section 5.6 Small Signal Model & Analysis. Quiz No 1 DE 27 (CE) State the purpose and four steps (each) that are to be taken for carrying out (a)DC Analysis](https://reader038.vdocuments.mx/reader038/viewer/2022102415/56649ec15503460f94bcd8fc/html5/thumbnails/63.jpg)
Summary : Common Collector
Non-unilateral Amplifier Input Resistance depends upon RL
Output Resistance depends upon Rsig
High Input Resistance
Low out Resistance
Voltage Gain ≈ unity
Relatively Large Current = 1+β
![Page 64: Section 5.6 Small Signal Model & Analysis. Quiz No 1 DE 27 (CE) State the purpose and four steps (each) that are to be taken for carrying out (a)DC Analysis](https://reader038.vdocuments.mx/reader038/viewer/2022102415/56649ec15503460f94bcd8fc/html5/thumbnails/64.jpg)
An equivalent circuit of the emitter follower
![Page 65: Section 5.6 Small Signal Model & Analysis. Quiz No 1 DE 27 (CE) State the purpose and four steps (each) that are to be taken for carrying out (a)DC Analysis](https://reader038.vdocuments.mx/reader038/viewer/2022102415/56649ec15503460f94bcd8fc/html5/thumbnails/65.jpg)
BJT Configurations
![Page 66: Section 5.6 Small Signal Model & Analysis. Quiz No 1 DE 27 (CE) State the purpose and four steps (each) that are to be taken for carrying out (a)DC Analysis](https://reader038.vdocuments.mx/reader038/viewer/2022102415/56649ec15503460f94bcd8fc/html5/thumbnails/66.jpg)
Common Emitter
![Page 67: Section 5.6 Small Signal Model & Analysis. Quiz No 1 DE 27 (CE) State the purpose and four steps (each) that are to be taken for carrying out (a)DC Analysis](https://reader038.vdocuments.mx/reader038/viewer/2022102415/56649ec15503460f94bcd8fc/html5/thumbnails/67.jpg)
Common Emitter with Emitter Resistance
![Page 68: Section 5.6 Small Signal Model & Analysis. Quiz No 1 DE 27 (CE) State the purpose and four steps (each) that are to be taken for carrying out (a)DC Analysis](https://reader038.vdocuments.mx/reader038/viewer/2022102415/56649ec15503460f94bcd8fc/html5/thumbnails/68.jpg)
Common Base : Current Buffer
![Page 69: Section 5.6 Small Signal Model & Analysis. Quiz No 1 DE 27 (CE) State the purpose and four steps (each) that are to be taken for carrying out (a)DC Analysis](https://reader038.vdocuments.mx/reader038/viewer/2022102415/56649ec15503460f94bcd8fc/html5/thumbnails/69.jpg)
Common Collector : Voltage Follower
![Page 70: Section 5.6 Small Signal Model & Analysis. Quiz No 1 DE 27 (CE) State the purpose and four steps (each) that are to be taken for carrying out (a)DC Analysis](https://reader038.vdocuments.mx/reader038/viewer/2022102415/56649ec15503460f94bcd8fc/html5/thumbnails/70.jpg)
Summary & Comparison
![Page 71: Section 5.6 Small Signal Model & Analysis. Quiz No 1 DE 27 (CE) State the purpose and four steps (each) that are to be taken for carrying out (a)DC Analysis](https://reader038.vdocuments.mx/reader038/viewer/2022102415/56649ec15503460f94bcd8fc/html5/thumbnails/71.jpg)
Comparison of Transistor Configurationsж
Quantity
Common Emitter (CE)
Common Collector (CC)
Common Base (CB)
AI Current Gain High (-50) High (50) Low (0.98)
AV Voltage Gain High (-136) Low (0.99) High (1.4)
Ri Input Resistance Medium (1 kΩ) High (154 kΩ) Low (21 Ω)
Ro
Output Resistance High (∞) Low (80 Ω) High (∞)
ж re = 1.1 kΩ, β = 50, RL= Rs = 3kΩ
![Page 72: Section 5.6 Small Signal Model & Analysis. Quiz No 1 DE 27 (CE) State the purpose and four steps (each) that are to be taken for carrying out (a)DC Analysis](https://reader038.vdocuments.mx/reader038/viewer/2022102415/56649ec15503460f94bcd8fc/html5/thumbnails/72.jpg)
Problem 5.135
• The amplifier of Fig. P5.135 consists of two identical common-emitter amplifier connected in cascade. Observe that the input resistance of the second stage, Rin2, constitutes the load resistance of the first stage.– For Vcc = 15V, R1 = 100kΩ , R2 = 47kΩ , RE = 3.9kΩ , Rc =
6.8kΩ , and β = 1000, determine the dc collector current and dc collector voltage of each transistor.
– Draw the small-signal equivalent circuit of the entire amplifier and give the values of all its components. Neglect ro1 and ro2
– Find Rin1 and vb1/vsig for Rsig = 5 kΩ– Find Rin2 and vb2/vb1.
– For RL = 2kΩ , find vo /vb2
– Find the overall voltage gain vo /vsig
![Page 73: Section 5.6 Small Signal Model & Analysis. Quiz No 1 DE 27 (CE) State the purpose and four steps (each) that are to be taken for carrying out (a)DC Analysis](https://reader038.vdocuments.mx/reader038/viewer/2022102415/56649ec15503460f94bcd8fc/html5/thumbnails/73.jpg)
Figure P5.135
![Page 74: Section 5.6 Small Signal Model & Analysis. Quiz No 1 DE 27 (CE) State the purpose and four steps (each) that are to be taken for carrying out (a)DC Analysis](https://reader038.vdocuments.mx/reader038/viewer/2022102415/56649ec15503460f94bcd8fc/html5/thumbnails/74.jpg)
Solution P5-135DC Analysis
Suppress the AC (independent Sources)Short Circuit Voltage Sources
Open Circuit the Capacitors
Calculate DC Node Voltages & Loop Currents
![Page 75: Section 5.6 Small Signal Model & Analysis. Quiz No 1 DE 27 (CE) State the purpose and four steps (each) that are to be taken for carrying out (a)DC Analysis](https://reader038.vdocuments.mx/reader038/viewer/2022102415/56649ec15503460f94bcd8fc/html5/thumbnails/75.jpg)
Solution P5-135DC Analysis
kR
VV
B
BB
32147
10047
8.41547100
47
VkIRVV
mAII
mAR
R
VVI
CCCCC
EC
BE
BEBBE
5.88.696.015
96.097.099.0
97.0
1
VmAV
Ig
T
Cm /8.3
•β=100, α=0.99
![Page 76: Section 5.6 Small Signal Model & Analysis. Quiz No 1 DE 27 (CE) State the purpose and four steps (each) that are to be taken for carrying out (a)DC Analysis](https://reader038.vdocuments.mx/reader038/viewer/2022102415/56649ec15503460f94bcd8fc/html5/thumbnails/76.jpg)
Small Signal Model
Suppress the DC (independent Sources)Short Circuit Voltage SourcesOpen Circuit Current Sources
Short Circuit the Capacitors
Draw the Small Signal Model
![Page 77: Section 5.6 Small Signal Model & Analysis. Quiz No 1 DE 27 (CE) State the purpose and four steps (each) that are to be taken for carrying out (a)DC Analysis](https://reader038.vdocuments.mx/reader038/viewer/2022102415/56649ec15503460f94bcd8fc/html5/thumbnails/77.jpg)
Small Signal Model
sigv
SR 1bv
1r
iv
C
1imvg
1CR1BR 2r
2imvg
2CR LR
ov
2inR1inR
![Page 78: Section 5.6 Small Signal Model & Analysis. Quiz No 1 DE 27 (CE) State the purpose and four steps (each) that are to be taken for carrying out (a)DC Analysis](https://reader038.vdocuments.mx/reader038/viewer/2022102415/56649ec15503460f94bcd8fc/html5/thumbnails/78.jpg)
krRRR
rr
kRR
kg
rr
kRR
Binin
oo
CC
m
BB
4.2||
8.6
6.2
32
121
21
21
21
21
sigv
SR 1bv
1r
iv
C
1imvg
1CR1BR 2r
2imvg
2CR LR
ov
2inR1inR
VVv
v
v
v
v
v
v
v
VVv
vRRvgv
VVv
v
RRvgv
VVRR
R
v
v
i
o
i
i
S
i
S
o
i
oLCimo
i
i
inCimi
Sin
in
sig
i
/1292..
/3.59||
/1.68
||
/32.0
21
21
222
1
2
2112
1
11
Small Signal Model
![Page 79: Section 5.6 Small Signal Model & Analysis. Quiz No 1 DE 27 (CE) State the purpose and four steps (each) that are to be taken for carrying out (a)DC Analysis](https://reader038.vdocuments.mx/reader038/viewer/2022102415/56649ec15503460f94bcd8fc/html5/thumbnails/79.jpg)
Figure P5.141 Common Base
For the circuit shown, Assume β=100
(a) Find the input resistance Rin
(b) Find the voltage gain vo/vsig
![Page 80: Section 5.6 Small Signal Model & Analysis. Quiz No 1 DE 27 (CE) State the purpose and four steps (each) that are to be taken for carrying out (a)DC Analysis](https://reader038.vdocuments.mx/reader038/viewer/2022102415/56649ec15503460f94bcd8fc/html5/thumbnails/80.jpg)
Figure P5.141 (Common Base)
DC Analysis
Suppress the AC (independent Sources)Short Circuit Voltage Sources
Open Circuit the Capacitors
Calculate DC Node Voltages & Loop Currents
![Page 81: Section 5.6 Small Signal Model & Analysis. Quiz No 1 DE 27 (CE) State the purpose and four steps (each) that are to be taken for carrying out (a)DC Analysis](https://reader038.vdocuments.mx/reader038/viewer/2022102415/56649ec15503460f94bcd8fc/html5/thumbnails/81.jpg)
Figure P5.141 (Common Base)
DC Analysis
Calculate DC Node Voltages & Loop Currents
IC
IB
IE
I = IB +IC=IE=0.33 mA
7533.0
25
E
T
E
T
T
Cme I
VI
V
VIg
r
β =100
![Page 82: Section 5.6 Small Signal Model & Analysis. Quiz No 1 DE 27 (CE) State the purpose and four steps (each) that are to be taken for carrying out (a)DC Analysis](https://reader038.vdocuments.mx/reader038/viewer/2022102415/56649ec15503460f94bcd8fc/html5/thumbnails/82.jpg)
Figure P5.141 (Common Base)
Small Signal Analysis
Suppress the DC (independent Sources)Short Circuit Voltage SourcesOpen Circuit Current Sources
Short Circuit the Capacitors
Draw the Small Signal Model
![Page 83: Section 5.6 Small Signal Model & Analysis. Quiz No 1 DE 27 (CE) State the purpose and four steps (each) that are to be taken for carrying out (a)DC Analysis](https://reader038.vdocuments.mx/reader038/viewer/2022102415/56649ec15503460f94bcd8fc/html5/thumbnails/83.jpg)
e
o
e
e
sig
e
sig
o
i
v
v
i
v
v
v
v
VVRr
r
v
v
sige
e
sig
e /5.0
7511
ee
e
rv
i
VVv
v
sig
o /9
Small Signal Analysis
75ein rR
)5.1||100(99.0)||( kkRRi
vLB
e
o
ic=αie
vo
B
C
E
veie
Rin
![Page 84: Section 5.6 Small Signal Model & Analysis. Quiz No 1 DE 27 (CE) State the purpose and four steps (each) that are to be taken for carrying out (a)DC Analysis](https://reader038.vdocuments.mx/reader038/viewer/2022102415/56649ec15503460f94bcd8fc/html5/thumbnails/84.jpg)
Figure P5.143 Common Collector ( Emitter follower)
For the circuit shown, Assume β=40
(a) Find IE,VE,& VB
(b) Find the input resistance Rin
(c) Find the voltage gain vo/vsig
![Page 85: Section 5.6 Small Signal Model & Analysis. Quiz No 1 DE 27 (CE) State the purpose and four steps (each) that are to be taken for carrying out (a)DC Analysis](https://reader038.vdocuments.mx/reader038/viewer/2022102415/56649ec15503460f94bcd8fc/html5/thumbnails/85.jpg)
Figure P5.143 Common Collector ( Emitter follower)
Suppress the AC (independent Sources)Short Circuit Voltage Sources
Open Circuit the Capacitors
Calculate DC Node Voltages & Loop Currents
![Page 86: Section 5.6 Small Signal Model & Analysis. Quiz No 1 DE 27 (CE) State the purpose and four steps (each) that are to be taken for carrying out (a)DC Analysis](https://reader038.vdocuments.mx/reader038/viewer/2022102415/56649ec15503460f94bcd8fc/html5/thumbnails/86.jpg)
Figure P5.143 Common Collector ( Emitter follower)
Calculate DC Node Voltages & Loop Currents
mARR
VVI
BE
BECCE 41.2
1
VRIV EEE 41.2
VVVV BEEB 11.3
β=40
37.10E
Te I
Vr
![Page 87: Section 5.6 Small Signal Model & Analysis. Quiz No 1 DE 27 (CE) State the purpose and four steps (each) that are to be taken for carrying out (a)DC Analysis](https://reader038.vdocuments.mx/reader038/viewer/2022102415/56649ec15503460f94bcd8fc/html5/thumbnails/87.jpg)
Figure P5.143 Common Collector ( Emitter follower)
Small Signal Analysis
Suppress the DC (independent Sources)Short Circuit Voltage SourcesOpen Circuit Current Sources
Short Circuit the Capacitors
Draw the Small Signal Model
![Page 88: Section 5.6 Small Signal Model & Analysis. Quiz No 1 DE 27 (CE) State the purpose and four steps (each) that are to be taken for carrying out (a)DC Analysis](https://reader038.vdocuments.mx/reader038/viewer/2022102415/56649ec15503460f94bcd8fc/html5/thumbnails/88.jpg)
Small Signal Model P5-143
![Page 89: Section 5.6 Small Signal Model & Analysis. Quiz No 1 DE 27 (CE) State the purpose and four steps (each) that are to be taken for carrying out (a)DC Analysis](https://reader038.vdocuments.mx/reader038/viewer/2022102415/56649ec15503460f94bcd8fc/html5/thumbnails/89.jpg)
3.17)||)(1(|| LEeBi RRrRR
b
o
sig
b
sig
o
v
v
v
v
v
v
isig
i
sig
b
RR
R
v
v
)||(
||
lce
Lc
b
o
RRr
RR
v
v
VVRRr
RR
RR
R
v
v
lce
Lc
isig
i
sig
o / 621.0)||(
||
Small Signal Model P5-143
Ri
(β+1)ib
vb
vo
![Page 90: Section 5.6 Small Signal Model & Analysis. Quiz No 1 DE 27 (CE) State the purpose and four steps (each) that are to be taken for carrying out (a)DC Analysis](https://reader038.vdocuments.mx/reader038/viewer/2022102415/56649ec15503460f94bcd8fc/html5/thumbnails/90.jpg)
![Page 91: Section 5.6 Small Signal Model & Analysis. Quiz No 1 DE 27 (CE) State the purpose and four steps (each) that are to be taken for carrying out (a)DC Analysis](https://reader038.vdocuments.mx/reader038/viewer/2022102415/56649ec15503460f94bcd8fc/html5/thumbnails/91.jpg)
Figure P5.144
![Page 92: Section 5.6 Small Signal Model & Analysis. Quiz No 1 DE 27 (CE) State the purpose and four steps (each) that are to be taken for carrying out (a)DC Analysis](https://reader038.vdocuments.mx/reader038/viewer/2022102415/56649ec15503460f94bcd8fc/html5/thumbnails/92.jpg)
Problem
![Page 93: Section 5.6 Small Signal Model & Analysis. Quiz No 1 DE 27 (CE) State the purpose and four steps (each) that are to be taken for carrying out (a)DC Analysis](https://reader038.vdocuments.mx/reader038/viewer/2022102415/56649ec15503460f94bcd8fc/html5/thumbnails/93.jpg)
Problem
![Page 94: Section 5.6 Small Signal Model & Analysis. Quiz No 1 DE 27 (CE) State the purpose and four steps (each) that are to be taken for carrying out (a)DC Analysis](https://reader038.vdocuments.mx/reader038/viewer/2022102415/56649ec15503460f94bcd8fc/html5/thumbnails/94.jpg)
Problem 5.147
• For the circuit in Fig P5.147, called a boot-strapped follower:– Find the dc emitter current and gm, re, and rΠ Use β =
100.
– Replace the BJT with its T model (neglecting ro), and analyze the circuit to determine the input resistance Rin and the voltage gain vo/vsig.
– Repeat (b) for the case when capacitor CB is open –circuited. Compare the results with those obtained in (b) to find the advantages of bootstrapping.
![Page 95: Section 5.6 Small Signal Model & Analysis. Quiz No 1 DE 27 (CE) State the purpose and four steps (each) that are to be taken for carrying out (a)DC Analysis](https://reader038.vdocuments.mx/reader038/viewer/2022102415/56649ec15503460f94bcd8fc/html5/thumbnails/95.jpg)
Boot-Strapped Follower
P5-147
![Page 96: Section 5.6 Small Signal Model & Analysis. Quiz No 1 DE 27 (CE) State the purpose and four steps (each) that are to be taken for carrying out (a)DC Analysis](https://reader038.vdocuments.mx/reader038/viewer/2022102415/56649ec15503460f94bcd8fc/html5/thumbnails/96.jpg)
Figure P5.147
DC Analysis
Suppress the AC (independent Sources)Short Circuit Voltage Sources
Open Circuit the Capacitors
Calculate DC Node Voltages & Loop Currents
![Page 97: Section 5.6 Small Signal Model & Analysis. Quiz No 1 DE 27 (CE) State the purpose and four steps (each) that are to be taken for carrying out (a)DC Analysis](https://reader038.vdocuments.mx/reader038/viewer/2022102415/56649ec15503460f94bcd8fc/html5/thumbnails/97.jpg)
Figure P5.147
DC Analysis
Calculate DC Node Voltages & Loop Currents
V9
V5.4
k10 k10
k2
EV
![Page 98: Section 5.6 Small Signal Model & Analysis. Quiz No 1 DE 27 (CE) State the purpose and four steps (each) that are to be taken for carrying out (a)DC Analysis](https://reader038.vdocuments.mx/reader038/viewer/2022102415/56649ec15503460f94bcd8fc/html5/thumbnails/98.jpg)
DC Analysis
mAII
mAk
I
RR
VVI
kR
VV
EC
E
BC
BEBBE
B
BB
71.1
73.1
101
10102
7.05.4
1
10
5.4
V9
V5.4
k10 k10
k2
EV
Solution 5-147
kg
r
gI
Vr
VmAV
I
V
Ig
m
mC
Te
T
E
T
Cm
46.1
5.145.68
99.0
73.1
25
/5.68
![Page 99: Section 5.6 Small Signal Model & Analysis. Quiz No 1 DE 27 (CE) State the purpose and four steps (each) that are to be taken for carrying out (a)DC Analysis](https://reader038.vdocuments.mx/reader038/viewer/2022102415/56649ec15503460f94bcd8fc/html5/thumbnails/99.jpg)
Figure P5.147
Small Signal Model
Suppress the DC (independent Sources)Short Circuit Voltage SourcesOpen Circuit Current Sources
Short Circuit the Capacitors
Draw the Small Signal Model
![Page 100: Section 5.6 Small Signal Model & Analysis. Quiz No 1 DE 27 (CE) State the purpose and four steps (each) that are to be taken for carrying out (a)DC Analysis](https://reader038.vdocuments.mx/reader038/viewer/2022102415/56649ec15503460f94bcd8fc/html5/thumbnails/100.jpg)
B
E
C
αie
Figure P5.147
Small Signal Model
re
![Page 101: Section 5.6 Small Signal Model & Analysis. Quiz No 1 DE 27 (CE) State the purpose and four steps (each) that are to be taken for carrying out (a)DC Analysis](https://reader038.vdocuments.mx/reader038/viewer/2022102415/56649ec15503460f94bcd8fc/html5/thumbnails/101.jpg)
B
E
C
αie
B
E
C
αie
ie
i
Rin
Solution 5-147
![Page 102: Section 5.6 Small Signal Model & Analysis. Quiz No 1 DE 27 (CE) State the purpose and four steps (each) that are to be taken for carrying out (a)DC Analysis](https://reader038.vdocuments.mx/reader038/viewer/2022102415/56649ec15503460f94bcd8fc/html5/thumbnails/102.jpg)
B
E
C
αie
ie
i
Rin
krRrR
i
vR
vii
vvi
iii
vR
eEeEb
in
be
bbe
e
bin
148.168))(1(1
)168148()99.01(
)48.1681()166748.14(
)1(
VVRR
R
rR
R
v
v
v
v
v
v
insig
in
eE
E
sig
b
bsig
/93.000
Solution 5-147
vo
![Page 103: Section 5.6 Small Signal Model & Analysis. Quiz No 1 DE 27 (CE) State the purpose and four steps (each) that are to be taken for carrying out (a)DC Analysis](https://reader038.vdocuments.mx/reader038/viewer/2022102415/56649ec15503460f94bcd8fc/html5/thumbnails/103.jpg)
kkR
kRR
krRrR
i
vR
ib
ibin
eEeEb
ib
12.18)20(
)20(
203))(1(1
Rib
VVRR
R
rR
R
v
v
v
v
v
v
insig
in
eE
E
sig
b
bsig
/64.000
Rin
The value of overall voltage gain and Rin obtained by using Bootstrap capacitor is higher than cct ,without BootstrappingBootstrapping is used to avoid loading of the input cct and to have higher gain.
Solution 5-147Without Boot-Strap Capacitor
![Page 104: Section 5.6 Small Signal Model & Analysis. Quiz No 1 DE 27 (CE) State the purpose and four steps (each) that are to be taken for carrying out (a)DC Analysis](https://reader038.vdocuments.mx/reader038/viewer/2022102415/56649ec15503460f94bcd8fc/html5/thumbnails/104.jpg)
Comparison of Transistor Configurations
Quantity
Common Emitter (CE)
Common Collector (CC)
Common Base (CB)
AI Current Gain High High Low
AV Voltage Gain High Low High
Ri Input Resistance Medium High Low
Ro Out Resistance High Low High