EE303 Electronics II
Topic 2
Dr Mohamad Rahal
Low Frequency Response of CS and
CE Amplifiers, High frequency
Response of Amps.
Microelectronic Circuits - Fifth Edition
Sedra/Smith
Copyright  2004 by Oxford University Press, Inc.
1
Outline of Topic 2
• Frequency Response of CS amplifier
• Frequency Response of CE amplifier
• High Frequency Response of CS and CE
amplifiers
Microelectronic Circuits - Fifth Edition
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Copyright  2004 by Oxford University Press, Inc.
2
Capacitively Coupled CS Amplifier
Microelectronic Circuits - Fifth Edition
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High-Frequency Behaviour
All the coupling
capacitors are
short circuits
I gd  SC gd (Vgs  Vo )
I gd  SC gd (Vgs  g m RL' Vgs )
I gd  SC gd (1  g m RL' )Vgs
I load  I gd  g mVgs
SCeqVgs  SC gd (1  g m RL' )Vgs
Ceq  C gd (1  g m RL' )
Microelectronic Circuits - Fifth Edition
I load  g mVgs
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Vo   g mVgs RL'
4
Bandwidth
Microelectronic Circuits - Fifth Edition
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5
Observations
'
Rsig
 RG // Rsig
C gd
'
Rsig
 Rsig
'
1

g
R
undergoes a multiplication by
m L Miller effect
The analysis was simplified by assuming that I gd << g mVgs
Try Out example 4.12 in the book.
Microelectronic Circuits - Fifth Edition
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Copyright  2004 by Oxford University Press, Inc.
6
Low Frequency Response of CS 1
1) First time constant
Microelectronic Circuits - Fifth Edition
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7
Low Frequency Response of CS 2
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Low Frequency Response of CS 3
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Overall Low Frequency Response
wP 2  g m  wP1 , wP3
Microelectronic Circuits - Fifth Edition
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10
Low Frequency Example CS
Microelectronic Circuits - Fifth Edition
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11
Frequency Response of CE Amplifier
Microelectronic Circuits - Fifth Edition
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12
High Frequency Response of CE 1
CE , CC1 , CC 2 are short circuits
Microelectronic Circuits - Fifth Edition
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13
High Frequency Response of CE 2
Close to
fH
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Observations for High frequency CE
• The Upper 3-dB frequency is determined by Cin
'
and Rsig
• Miller effect reduces the bandwidth due to
(1  g m R )C
'
L
• The assumption is an approximation due to
I   g mV
• We have neglected the effect of any load
capacitance
Microelectronic Circuits - Fifth Edition
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15
CE Example
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16
Low Frequency CE 1
C , C are open circuits
ro
neglected
Other capacitors
Are shorted
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Low Frequency CE 2
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Low Frequency CE 3
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Low Frequency CE 4
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Low Frequency CE 5
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Overall Low Frequency of CE
Try out Example 5.19
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End of Topic 2
Lectures
Home work 2: 4.94, 4.97, 4.99, 5.157, 5.159, 5.167,
6.66, 6.69, 6.70
Materials can be found on the Y:\EE303-001
Please check this folder on a daily/weekly basis
Microelectronic Circuits - Fifth Edition
Sedra/Smith
Copyright  2004 by Oxford University Press, Inc.
23