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ELZ 303 - Elektronik II
Dr. Mehmet Siraç Özerdem
Elektrik Elektronik Müh. Bölümü
Dicle Universitesi
Microelectronic Circuits – Fourth Edition
Adel S. Sedra, Kenneth C. Smith, 1998 Oxford University Press
Copyright 2004 by Oxford University Press, Inc.
Feedback
Microelectronic Circuits - Fifth Edition Sedra/Smith
General structure of the feedback amplifier. This is a
signal-flow diagram, and the quantities x represent either
voltage or current signals.
2
Copyright 2004 by Oxford University Press, Inc.Microelectronic Circuits - Fifth Edition Sedra/Smith
Feedback
A : Open loop gain (AOL)
Af : Closed loop gain
: Feedback factor
1+ A : Amount of feedback
Copyright 2004 by Oxford University Press, Inc.Microelectronic Circuits - Fifth Edition Sedra/Smith
Example : Non inverting op-amp
(ideal Op-amp => Ri → and Ro=0)
a) =?
b) A=104 and Af = 10, R2/R1=?
c) Amount of feedback in dB = ?
3
Copyright 2004 by Oxford University Press, Inc.Microelectronic Circuits - Fifth Edition Sedra/Smith
Feedback
Illustrating the application of negative feedback to
improve the signal-to-noise ratio in amplifiers.
Copyright 2004 by Oxford University Press, Inc.Microelectronic Circuits - Fifth Edition Sedra/Smith
Illustrating the application of negative feedback to reduce
the nonlinear distortion in amplifiers.
Curve (a) shows the amplifier transfer characteristic
without feedback.
Curve (b) shows the characteristic with negative
feedback ( 0.01) applied.
Feedback
4
Copyright 2004 by Oxford University Press, Inc.Microelectronic Circuits - Fifth Edition Sedra/Smith
current-mixing voltage-sampling
(shunt–shunt) topology
The four basic feedback topologies
voltage-mixing voltage-sampling
(series–shunt) topology
current-mixing current-sampling
(shunt–series) topology
voltage-mixing current-sampling
(series–series) topology
Feedback :
Copyright 2004 by Oxford University Press, Inc.Microelectronic Circuits - Fifth Edition Sedra/Smith
Example
A transistor amplifier with shunt–series feedback.
(Biasing not shown.)
5
Copyright 2004 by Oxford University Press, Inc.Microelectronic Circuits - Fifth Edition Sedra/Smith
An example of the series–series feedback topology.
(Biasing not shown.)
Example
Copyright 2004 by Oxford University Press, Inc.Microelectronic Circuits - Fifth Edition Sedra/Smith
Example
(a) The inverting op-amp configuration redrawn as
(b) an example of shunt–shunt feedback
6
Copyright 2004 by Oxford University Press, Inc.Microelectronic Circuits - Fifth Edition Sedra/Smith
1. The series–shunt feedback amplifier
ideal structure equivalent circuit.
Copyright 2004 by Oxford University Press, Inc.Microelectronic Circuits - Fifth Edition Sedra/Smith
1. The series–shunt feedback amplifier
7
Copyright 2004 by Oxford University Press, Inc.Microelectronic Circuits - Fifth Edition Sedra/Smith
1. The series–shunt feedback amplifier (The practical situation)
Derivation of the A circuit and circuit for the series–shunt feedback amplifier.
Block diagram of a practical series–shunt feedback
amplifier
Copyright 2004 by Oxford University Press, Inc.Microelectronic Circuits - Fifth Edition Sedra/Smith
Two-Port
Network
h parameters
8
Copyright 2004 by Oxford University Press, Inc.Microelectronic Circuits - Fifth Edition Sedra/Smith
1. The series–shunt feedback amplifier (The practical situation)
The circuit with the feedback network represented by
its h parameters
Copyright 2004 by Oxford University Press, Inc.Microelectronic Circuits - Fifth Edition Sedra/Smith
1. The series–shunt feedback amplifier (The practical situation)
9
Copyright 2004 by Oxford University Press, Inc.Microelectronic Circuits - Fifth Edition Sedra/Smith1
. T
he
seri
es–
shu
nt
feed
ba
ck a
mp
lifi
er
(Summary)
Copyright 2004 by Oxford University Press, Inc.Microelectronic Circuits - Fifth Edition Sedra/Smith
Example
μ= 104
Rid=100k
ro=1k
RL=2k
R1=1k
R2=1M
Rs=10k
A=?
= ?
Af = (Vo/Vs) = ?
Rin = ?
Rout = ?
10
Copyright 2004 by Oxford University Press, Inc.Microelectronic Circuits - Fifth Edition Sedra/Smith
Example (continued)
Copyright 2004 by Oxford University Press, Inc.Microelectronic Circuits - Fifth Edition Sedra/Smith
2. The series–series feedback amplifier
ideal structure
equivalent circuit
11
Copyright 2004 by Oxford University Press, Inc.Microelectronic Circuits - Fifth Edition Sedra/Smith
2. The series–series feedback amplifier
Copyright 2004 by Oxford University Press, Inc.Microelectronic Circuits - Fifth Edition Sedra/Smith
2. The series–series feedback amplifier (The practical situation)
Derivation of the A circuit and circuit for the series–shunt feedback amplifier.
Block diagram of a practical series–series feedback
amplifier
12
Copyright 2004 by Oxford University Press, Inc.Microelectronic Circuits - Fifth Edition Sedra/Smith
Two-Port
Network
z parameters
Copyright 2004 by Oxford University Press, Inc.Microelectronic Circuits - Fifth Edition Sedra/Smith
2. The series–series feedback amplifier (The practical situation)
The circuit with the feedback network represented by
its z parameters
13
Copyright 2004 by Oxford University Press, Inc.Microelectronic Circuits - Fifth Edition Sedra/Smith
2. The series–series feedback amplifier (The practical situation)
Copyright 2004 by Oxford University Press, Inc.Microelectronic Circuits - Fifth Edition Sedra/Smith2
. T
he
seri
es–
seri
es f
eed
ba
ck a
mp
lifi
er
(Summary)
14
Copyright 2004 by Oxford University Press, Inc.Microelectronic Circuits - Fifth Edition Sedra/Smith
Example
IC1=0.6mA
IC2=1mA
IC3=4mA
hfe=100
ro →
A=?
= ?
Af = (Io/Vs) = ?
Vo/Vs = ?
Rin = Rif = ?
Rof = ?
Copyright 2004 by Oxford University Press, Inc.Microelectronic Circuits - Fifth Edition Sedra/Smith
Example (continued)
15
Copyright 2004 by Oxford University Press, Inc.Microelectronic Circuits - Fifth Edition Sedra/Smith
Example (continued)
Calculation of
Calculation of Rout
Copyright 2004 by Oxford University Press, Inc.Microelectronic Circuits - Fifth Edition Sedra/Smith
3. The shunt–shunt feedback amplifier
ideal structure
16
Copyright 2004 by Oxford University Press, Inc.Microelectronic Circuits - Fifth Edition Sedra/Smith
3. The shunt–shunt feedback amplifier
Copyright 2004 by Oxford University Press, Inc.Microelectronic Circuits - Fifth Edition Sedra/Smith
3. The shunt–shunt feedback amplifier (The practical situation)
Derivation of the A circuit and circuit for the series–shunt feedback amplifier.
Block diagram of a practical shunt–shunt feedback
amplifier
17
Copyright 2004 by Oxford University Press, Inc.Microelectronic Circuits - Fifth Edition Sedra/Smith
Two-Port
Network
y parameters
Copyright 2004 by Oxford University Press, Inc.Microelectronic Circuits - Fifth Edition Sedra/Smith3
. T
he
shu
nt–
shu
nt
feed
ba
ck a
mp
lifi
er
(Summary)
18
Copyright 2004 by Oxford University Press, Inc.Microelectronic Circuits - Fifth Edition Sedra/Smith
Example
= 100
VBE = 0.7 V
Vo/Vs = ?
Rin = ?
Rout = ?
Copyright 2004 by Oxford University Press, Inc.Microelectronic Circuits - Fifth Edition Sedra/Smith
Example (continued)
19
Copyright 2004 by Oxford University Press, Inc.Microelectronic Circuits - Fifth Edition Sedra/Smith
Example (continued)
Copyright 2004 by Oxford University Press, Inc.Microelectronic Circuits - Fifth Edition Sedra/Smith
4. The shunt–series feedback amplifier
ideal structure
20
Copyright 2004 by Oxford University Press, Inc.Microelectronic Circuits - Fifth Edition Sedra/Smith
4. The shunt–series feedback amplifier
Copyright 2004 by Oxford University Press, Inc.Microelectronic Circuits - Fifth Edition Sedra/Smith
4. The shunt–series feedback amplifier (The practical situation)
Derivation of the A circuit and circuit for the series–shunt feedback amplifier.
Block diagram of a practical shunt–series feedback
amplifier
21
Copyright 2004 by Oxford University Press, Inc.Microelectronic Circuits - Fifth Edition Sedra/Smith
Two-Port
Network
g parameters
Copyright 2004 by Oxford University Press, Inc.Microelectronic Circuits - Fifth Edition Sedra/Smith4
. T
he
shu
nt-
seri
es f
eed
ba
ck a
mp
lifi
er
(Summary)
22
Copyright 2004 by Oxford University Press, Inc.Microelectronic Circuits - Fifth Edition Sedra/Smith
Example
= 100
VA = 75 V
Iout/Iin = ?
Rin = ?
Rout = ?
Copyright 2004 by Oxford University Press, Inc.Microelectronic Circuits - Fifth Edition Sedra/Smith
Example (continued)