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25.04.2011
1
Microelectronics Circuit Analysis and Design
Donald A. Neamen
Chapter 7
Frequency Response
Neamen Microelectronics, 4e Chapter 7-1McGraw-Hill
In this chapter, we will:
Discuss the general frequency response characteristics of amplifiers.
Derive the system transfer functions Derive the system transfer functions Develop the Bode diagrams of the magnitude
and phase of the transfer functions. Analyze the frequency response of transistor
circuits with capacitors. Determine the Miller effect and Miller
capacitance
Neamen Microelectronics, 4e Chapter 7-2McGraw-Hill
capacitance. Determine the high-frequency response of basic
transistor circuit configurations.
25.04.2011
2
Amplifier Gain Versus Frequency
Neamen Microelectronics, 4e Chapter 7-3McGraw-Hill
Transfer Functions of the Complex Frequency
Name of Function Expressionp
Voltage Transfer Function T(s) = Vo(s)/Vi(s)
Current Transfer Function Io(s)/Ii(s)
Transresistance Function V (s)/I (s)
Neamen Microelectronics, 4e Chapter 7-4McGraw-Hill
Transresistance Function Vo(s)/Ii(s)
Transconductance Function Io(s)/Vi(s)
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3
Series Coupling Capacitor Circuit
SPS CRRs
sKsT
)(
)1
()( 2
Neamen Microelectronics, 4e Chapter 7-5McGraw-Hill
Parallel Load Capacitor Circuit
PPS CRRs
KsT
)(
)1
1()( 1
Neamen Microelectronics, 4e Chapter 7-6McGraw-Hill
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4
Bode Plot of Voltage Transfer Function Magnitude:
Series Coupling Capacitor Circuit
Neamen Microelectronics, 4e Chapter 7-7McGraw-Hill
Relationship Between Rectangular and Polar Coordinates
Neamen Microelectronics, 4e Chapter 7-8McGraw-Hill
25.04.2011
5
Bode Plot of Voltage Transfer Function Phase:
Series Coupling Capacitor Circuit
Neamen Microelectronics, 4e Chapter 7-9McGraw-Hill
Bode Plot of Voltage Transfer Function Magnitude:
Parallel Load Capacitor Circuit
Neamen Microelectronics, 4e Chapter 7-10McGraw-Hill
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6
Bode Plot of Voltage Transfer Function Phase:
Parallel Load Capacitor Circuit
Neamen Microelectronics, 4e Chapter 7-11McGraw-Hill
Circuit with Series Coupling and Parallel Load Capacitor
SL
PPSP
SPSS
f
CRR
CRR
1
2
1
)(
)(
Neamen Microelectronics, 4e Chapter 7-12McGraw-Hill
PHf 2
1
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7
Bode Plot of Magnitude of Voltage Transfer Function:
Series Coupling and Parallel Load Capacitor
Neamen Microelectronics, 4e Chapter 7-13McGraw-Hill
Steady-State Output Response
Neamen Microelectronics, 4e Chapter 7-14McGraw-Hill
Coupling Capacitor Load Capacitor
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8
Common Emitter with Coupling Capacitor
L CRRf
)(2
1
CiSi CRR )(2
Neamen Microelectronics, 4e Chapter 7-15McGraw-Hill
Common Source with Output Coupling Capacitor
f1
CCDL CRR
f)(2
Neamen Microelectronics, 4e Chapter 7-16McGraw-Hill
25.04.2011
9
Emitter Follower with Output Coupling Capacitor
)(2
1L CRR
f 2)(2 CLo
L CRRf
Neamen Microelectronics, 4e Chapter 7-17McGraw-Hill
Problem-Solving Technique: Bode Plot of Gain Magnitude
1 Determine whether capacitor is producing a 1. Determine whether capacitor is producing a low-pass or high-pass circuit.a. Sketch general shape of Bode plot
2. Corner frequency is f = 1/(2) where = ReqCa. Req is resistance seen by capacitor
3. Maximum gain magnitude is midband gain.
Neamen Microelectronics, 4e Chapter 7-18McGraw-Hill
a. Coupling and bypass capacitors act as shorts
b. Load capacitors act as opens
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Common Source with Load Capacitor
LLoH CRR
f)(2
1
LLo
Neamen Microelectronics, 4e Chapter 7-19McGraw-Hill
Coupling and Parallel Load Capacitors
Neamen Microelectronics, 4e Chapter 7-20McGraw-Hill
25.04.2011
11
Small-Signal Equivalent Circuit:Coupling and Parallel Load Capacitor
Neamen Microelectronics, 4e Chapter 7-21McGraw-Hill
CiS
LCRRRR
f)]([2
1
21
PLCH CRR
f)(2
1
Emitter Bypass Capacitor
Neamen Microelectronics, 4e Chapter 7-22McGraw-Hill
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12
Bode Plot of Voltage Gain Magnitude: Emitter Bypass Capacitor
Neamen Microelectronics, 4e Chapter 7-23McGraw-Hill
rR
RrgA
RrR
RrgA
S
Cmv
ES
Cmv
)1(0
Two Coupling Capacitors and a Emitter Bypass Capacitor
Neamen Microelectronics, 4e Chapter 7-24McGraw-Hill
25.04.2011
13
PSpice Results for Two Coupling Capacitors and a Emitter Bypass
Capacitor
Neamen Microelectronics, 4e Chapter 7-25McGraw-Hill
Expanded Hybrid Equivalent Circuit
Neamen Microelectronics, 4e Chapter 7-26McGraw-Hill
25.04.2011
14
Short-Circuit Current Gain: Analysis of Frequency Response of BJT
Neamen Microelectronics, 4e Chapter 7-27McGraw-Hill
Bode Plot:Short-Circuit Current Gain
Neamen Microelectronics, 4e Chapter 7-28McGraw-Hill
ffCCr
f oT
)( 2
1
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15
2-Port Equivalent Circuit of CBJT
Neamen Microelectronics, 4e Chapter 7-29McGraw-Hill
Thevenin Equivalent Norton Equivalent
Small-Signal Equivalent Circuit with Miller Capacitance: BJT
Neamen Microelectronics, 4e Chapter 7-30McGraw-Hill
)](1[ LCmM RRgCC
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16
Inherent Resistances and Capacitances in n-Channel MOSFET
Neamen Microelectronics, 4e Chapter 7-31McGraw-Hill
oxgdgs WLCCC2
1
Equivalent Circuit for n-Channel Common Source MOSFET
Neamen Microelectronics, 4e Chapter 7-32McGraw-Hill
25.04.2011
17
Unity-Gain Bandwidth
Neamen Microelectronics, 4e Chapter 7-33McGraw-Hill
)(2 gdgs
mT CC
gf
Small-Signal Equivalent Circuit with Miller Capacitance: MOSFET
]1[ LmgdM RgCC
Neamen Microelectronics, 4e Chapter 7-34McGraw-Hill
25.04.2011
18
Common-Emitter Amplifier
Neamen Microelectronics, 4e Chapter 7-35McGraw-Hill
High-Frequency Equivalent Circuit:Common Emitter
Neamen Microelectronics, 4e Chapter 7-36McGraw-Hill
)]([2
1
CCRRrf
SBH
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PSpice Results for Common Emitter
Neamen Microelectronics, 4e Chapter 7-37McGraw-Hill
Common-Base Amplifier
Neamen Microelectronics, 4e Chapter 7-38McGraw-Hill
25.04.2011
20
High-Frequency Equivalent Circuit:Common Base
Neamen Microelectronics, 4e Chapter 7-39McGraw-Hill
CRR
rf
SB
H
]1
[2
1
CRR
fLC
H )(2
1
PSpice Results for Common Emitter
Neamen Microelectronics, 4e Chapter 7-40McGraw-Hill
25.04.2011
21
Cascode Circuit
Neamen Microelectronics, 4e Chapter 7-41McGraw-Hill
High-Frequency Equivalent Circuit:Cascode
Neamen Microelectronics, 4e Chapter 7-42McGraw-Hill
)]([2
1
1111 MBSH CCrRR
f
2)(2
1
CRR
fLC
H
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22
PSpice Results for Cascode
Neamen Microelectronics, 4e Chapter 7-43McGraw-Hill
Emitter-Follower Circuit
Neamen Microelectronics, 4e Chapter 7-44McGraw-Hill
25.04.2011
23
High-Frequency Equivalent Circuit:Emitter Follower
1Hf
Neamen Microelectronics, 4e Chapter 7-45McGraw-Hill
)1
]()1([2'
'
LmLmBS
H
Rg
CCrRgRR
f
PSpice Results for Emitter Follower
Neamen Microelectronics, 4e Chapter 7-46McGraw-Hill
