32
ECE 342 – Jose Schutt‐Aine 1 ECE 342 Electronic Circuits Lecture 28 Feedback Topologies Jose E. Schutt-Aine Electrical & Computer Engineering University of Illinois [email protected]
ECE 342 – Jose Schutt‐Aine 1
ECE 342Electronic Circuits
Lecture 28Feedback Topologies
Jose E. Schutt-AineElectrical & Computer Engineering
University of [email protected]
ECE 342 – Jose Schutt‐Aine 2
Series-Shunt Feedback
Voltage mixing-voltage sampling feedback
ECE 342 – Jose Schutt‐Aine 3
Shunt- Series Feedback
Current mixing-current sampling feedback
ECE 342 – Jose Schutt‐Aine 4
Series-Series Feedback
Voltage mixing-current sampling feedback
ECE 342 – Jose Schutt‐Aine 5
Shunt-Shunt Feedback
Current mixing-voltage sampling feedback
ECE 342 – Jose Schutt‐Aine 6
Transfer Function Representation
Use a two-terminal representation of system for input and output
ECE 342 – Jose Schutt‐Aine 7
Y-parameter Representation
1 11 1 12 2
2 21 1 22 2
I y V y VI y V y V
ECE 342 – Jose Schutt‐Aine 8
Y Parameter Calculations
2 2
1 211 21
1 10 0V V
I Iy yV V
To make V2= 0, place a short at port 2
ECE 342 – Jose Schutt‐Aine 9
Z Parameters
1 11 1 12 2
2 21 1 22 2
V z I z IV z I z I
ECE 342 – Jose Schutt‐Aine 10
Z-parameter Calculations
2 2
1 211 21
1 10 0I I
V Vz zI I
To make I2= 0, place an open at port 2
ECE 342 – Jose Schutt‐Aine 11
H Parameters
1 11 1 12 2
2 21 1 22 2
V h I h VI h I h V
ECE 342 – Jose Schutt‐Aine 12
H Parameter Calculations
To make V2= 0, place a short at port 2
2 2
1 211 21
1 10 0V V
V Ih hI I
ECE 342 – Jose Schutt‐Aine 13
G Parameters
1 11 1 12 2
2 21 1 22 2
I g V g IV g V g I
ECE 342 – Jose Schutt‐Aine 14
G-Parameter Calculations
2 2
1 211 21
1 10 0I I
I Vg gV V
To make I2= 0, place an open at port 2
ECE 342 – Jose Schutt‐Aine 15
Series-Shunt Feedback - Ideal
1o
fs
V AAV A
Negative feedback decreases the gain
o
i
VAV
ECE 342 – Jose Schutt‐Aine 16
Series-Shunt Feedback – Equivalent Circuit
1if iR R A
Negative feedback increases the input resistance and decreases the output resistance by a factor equal to the feedback
/ 1of oR R A
ECE 342 – Jose Schutt‐Aine 17
Series-Shunt Feedback - Actual
ECE 342 – Jose Schutt‐Aine 18
Series-Shunt Feedback : h-Parameters
Account for all 4 h parameters
ECE 342 – Jose Schutt‐Aine 19
Series-Shunt Feedback : h-Parameters
12 12basic feedbackamplifier network
h h 21 21feedback basicnetwork amplifier
h h
ECE 342 – Jose Schutt‐Aine 20
Series-Series Feedback - Ideal
1o
fs
I AAV A
Negative feedback decreases the gain
o
i
IAV
ECE 342 – Jose Schutt‐Aine 21
Series-Series Feedback – Equivalent Circuit
1if iR R A 1of oR R A
Negative feedback increases the input resistance and increases the output resistance by a factor equal to the feedback
ECE 342 – Jose Schutt‐Aine 22
Series-Series Feedback - Actual
ECE 342 – Jose Schutt‐Aine 23
Series-Series Feedback: Z Parameters
Account for all 4 z parameters
ECE 342 – Jose Schutt‐Aine 24
12 12basic feedbackamplifier network
z z21 21feedback basic
network amplifierz z
Series-Series Feedback: Z Parameters
ECE 342 – Jose Schutt‐Aine 25
Shunt-Shunt Feedback - Ideal
o
i
VAI
ECE 342 – Jose Schutt‐Aine 26
Shunt-Shunt Feedback
/ 1if iR R A / 1of oR R A
Negative feedback decreases the input resistance and decreases the output resistance by a factor equal to the feedback
12 12basic feedbackamplifier network
y y 21 21feedback basicnetwork amplifier
y y
1o
fs
V AAI A
Negative feedback decreases the gain
ECE 342 – Jose Schutt‐Aine 27
Shunt-Series Feedback - Ideal
o
i
IAI
ECE 342 – Jose Schutt‐Aine 28
Shunt-Series Feedback
/ 1if iR R A 1of oR R A
Negative feedback decreases the input resistance and increases the output resistance by a factor equal to the feedback
1o
fs
I AAI A
Negative feedback decreases the gain
12 12basic feedbackamplifier network
g g 21 21feedback basicnetwork amplifier
g g
ECE 342 – Jose Schutt‐Aine 29
Rules for Series-Shunt Feedback
1 11 1 12 2
2 21 1 22 2
V h I h VI h I h V
2 2
1 211 21
1 10 0V V
V Ih hI I
1 1
1 212 22
2 20 0
I I
V Ih hV V
ECE 342 – Jose Schutt‐Aine 30
Rules for Series-Series Feedback
1 11 1 12 2
2 21 1 22 2
V z I z IV z I z I
2 2
1 211 21
1 10 0I I
V Vz zI I
1 1
1 212 22
2 20 0
I I
V Vz zI I
ECE 342 – Jose Schutt‐Aine 31
Rules for Shunt-Shunt Feedback
2 2
1 211 21
1 10 0V V
I Iy yV V
1 11 1 12 2
2 21 1 22 2
I y V y VI y V y V
1 1
1 212 22
2 20 0
V V
I Iy yV V
ECE 342 – Jose Schutt‐Aine 32
Rules for Shunt-Series Feedback
1 11 1 12 2
2 21 1 22 2
I g V g IV g V g I
2 2
1 211 21
1 10 0I I
I Vg gV V
1 1
1 212 22
2 20 0
V V
I Vg gI I
