feedback amplifiers 16bu.edu.eg/portal/uploads/engineering, shoubra...feedback amplifier...
TRANSCRIPT
![Page 1: Feedback Amplifiers 16bu.edu.eg/portal/uploads/Engineering, Shoubra...Feedback Amplifier •Depending on the relative polarity of the signal being fed back into a circuit, one may](https://reader030.vdocument.in/reader030/viewer/2022040602/5e9b20117c38ad2a541939a4/html5/thumbnails/1.jpg)
Lecture #14 Feedback Amplifiers
Instructor: Dr. Ahmad El-Banna
Benha University Faculty of Engineering at Shoubra
Fa
ll 20
16
ECE-322 Electronic Circuits (A)
© A
hmad
El-B
anna
![Page 2: Feedback Amplifiers 16bu.edu.eg/portal/uploads/Engineering, Shoubra...Feedback Amplifier •Depending on the relative polarity of the signal being fed back into a circuit, one may](https://reader030.vdocument.in/reader030/viewer/2022040602/5e9b20117c38ad2a541939a4/html5/thumbnails/2.jpg)
Agenda
FB Amplifiers Structure
Different Topologies
Examples
Practical Feedback Circuits 2
Elec.
Cts A
, Lec
#14
, Fall
201
6 ©
Ahm
ad E
l-Ban
na
![Page 3: Feedback Amplifiers 16bu.edu.eg/portal/uploads/Engineering, Shoubra...Feedback Amplifier •Depending on the relative polarity of the signal being fed back into a circuit, one may](https://reader030.vdocument.in/reader030/viewer/2022040602/5e9b20117c38ad2a541939a4/html5/thumbnails/3.jpg)
FEEDBACK AMPLIFIER BASICS 3
© A
hmad
El-B
anna
Ele
c. Ct
s A , L
ec#1
4 , F
all 2
016
![Page 4: Feedback Amplifiers 16bu.edu.eg/portal/uploads/Engineering, Shoubra...Feedback Amplifier •Depending on the relative polarity of the signal being fed back into a circuit, one may](https://reader030.vdocument.in/reader030/viewer/2022040602/5e9b20117c38ad2a541939a4/html5/thumbnails/4.jpg)
Feedback Amplifier
4
• Block diagram of a typical feedback amplifier
• Types: 1. Negative feedback. 2. Positive feedback.
© A
hmad
El-B
anna
Ele
c. Ct
s A , L
ec#1
4 , F
all 2
016
![Page 5: Feedback Amplifiers 16bu.edu.eg/portal/uploads/Engineering, Shoubra...Feedback Amplifier •Depending on the relative polarity of the signal being fed back into a circuit, one may](https://reader030.vdocument.in/reader030/viewer/2022040602/5e9b20117c38ad2a541939a4/html5/thumbnails/5.jpg)
Feedback Amplifier
• Depending on the relative polarity of the signal being fed back into a circuit, one may have negative or positive feedback.
• Positive feedback drives a circuit into oscillation as in various types of oscillator circuits.
• Negative feedback results in decreased voltage gain, for which a number of circuit features are improved.
• Some improvements of negative feedback are : 1. Higher input impedance. 2. Lower output impedance. 3. Better stabilized voltage gain. 4. Improved frequency response. 5. Reduced noise. 6. More linear operation.
5
© A
hmad
El-B
anna
Ele
c. Ct
s A , L
ec#1
4 , F
all 2
016
![Page 6: Feedback Amplifiers 16bu.edu.eg/portal/uploads/Engineering, Shoubra...Feedback Amplifier •Depending on the relative polarity of the signal being fed back into a circuit, one may](https://reader030.vdocument.in/reader030/viewer/2022040602/5e9b20117c38ad2a541939a4/html5/thumbnails/6.jpg)
FEEDBACK CONNECTION TYPES
6
1. Voltage-series feedback 2. Voltage-shunt feedback
© A
hmad
El-B
anna
Ele
c. Ct
s A , L
ec#1
4 , F
all 2
016
![Page 7: Feedback Amplifiers 16bu.edu.eg/portal/uploads/Engineering, Shoubra...Feedback Amplifier •Depending on the relative polarity of the signal being fed back into a circuit, one may](https://reader030.vdocument.in/reader030/viewer/2022040602/5e9b20117c38ad2a541939a4/html5/thumbnails/7.jpg)
FEEDBACK CONNECTION TYPES..
7
3. Current-series feedback 4. Current-shunt feedback
© A
hmad
El-B
anna
Ele
c. Ct
s A , L
ec#1
4 , F
all 2
016
![Page 8: Feedback Amplifiers 16bu.edu.eg/portal/uploads/Engineering, Shoubra...Feedback Amplifier •Depending on the relative polarity of the signal being fed back into a circuit, one may](https://reader030.vdocument.in/reader030/viewer/2022040602/5e9b20117c38ad2a541939a4/html5/thumbnails/8.jpg)
Parameters improvement
8
© A
hmad
El-B
anna
Ele
c. Ct
s A , L
ec#1
4 , F
all 2
016
Effect of feedback on gain:
![Page 9: Feedback Amplifiers 16bu.edu.eg/portal/uploads/Engineering, Shoubra...Feedback Amplifier •Depending on the relative polarity of the signal being fed back into a circuit, one may](https://reader030.vdocument.in/reader030/viewer/2022040602/5e9b20117c38ad2a541939a4/html5/thumbnails/9.jpg)
Parameters improvement ..
9
© A
hmad
El-B
anna
Ele
c. Ct
s A , L
ec#1
4 , F
all 2
016
![Page 10: Feedback Amplifiers 16bu.edu.eg/portal/uploads/Engineering, Shoubra...Feedback Amplifier •Depending on the relative polarity of the signal being fed back into a circuit, one may](https://reader030.vdocument.in/reader030/viewer/2022040602/5e9b20117c38ad2a541939a4/html5/thumbnails/10.jpg)
FEEDBACK CONNECTION TYPES…
• Series feedback connections tend to increase the input resistance, whereas shunt feed-back connections tend to decrease the input resistance.
• Voltage feedback tends to decrease the output impedance, whereas current feedback tends to increase the output impedance.
10
© A
hmad
El-B
anna
Ele
c. Ct
s A , L
ec#1
4 , F
all 2
016
![Page 11: Feedback Amplifiers 16bu.edu.eg/portal/uploads/Engineering, Shoubra...Feedback Amplifier •Depending on the relative polarity of the signal being fed back into a circuit, one may](https://reader030.vdocument.in/reader030/viewer/2022040602/5e9b20117c38ad2a541939a4/html5/thumbnails/11.jpg)
Example
11
© A
hmad
El-B
anna
Ele
c. Ct
s A , L
ec#1
4 , F
all 2
016
![Page 12: Feedback Amplifiers 16bu.edu.eg/portal/uploads/Engineering, Shoubra...Feedback Amplifier •Depending on the relative polarity of the signal being fed back into a circuit, one may](https://reader030.vdocument.in/reader030/viewer/2022040602/5e9b20117c38ad2a541939a4/html5/thumbnails/12.jpg)
Practical Feedback Circuits
12
© A
hmad
El-B
anna
Ele
c. Ct
s A , L
ec#1
4 , F
all 2
016
Voltage-Series Feedback
![Page 13: Feedback Amplifiers 16bu.edu.eg/portal/uploads/Engineering, Shoubra...Feedback Amplifier •Depending on the relative polarity of the signal being fed back into a circuit, one may](https://reader030.vdocument.in/reader030/viewer/2022040602/5e9b20117c38ad2a541939a4/html5/thumbnails/13.jpg)
Voltage-Series Feedback circuit
13
© A
hmad
El-B
anna
Ele
c. Ct
s A , L
ec#1
4 , F
all 2
016
![Page 14: Feedback Amplifiers 16bu.edu.eg/portal/uploads/Engineering, Shoubra...Feedback Amplifier •Depending on the relative polarity of the signal being fed back into a circuit, one may](https://reader030.vdocument.in/reader030/viewer/2022040602/5e9b20117c38ad2a541939a4/html5/thumbnails/14.jpg)
Current-Series Feedback circuit
14
© A
hmad
El-B
anna
Ele
c. Ct
s A , L
ec#1
4 , F
all 2
016
![Page 15: Feedback Amplifiers 16bu.edu.eg/portal/uploads/Engineering, Shoubra...Feedback Amplifier •Depending on the relative polarity of the signal being fed back into a circuit, one may](https://reader030.vdocument.in/reader030/viewer/2022040602/5e9b20117c38ad2a541939a4/html5/thumbnails/15.jpg)
15
© A
hmad
El-B
anna
Ele
c. Ct
s A , L
ec#1
4 , F
all 2
016
Current-Series Feedback circuit
![Page 16: Feedback Amplifiers 16bu.edu.eg/portal/uploads/Engineering, Shoubra...Feedback Amplifier •Depending on the relative polarity of the signal being fed back into a circuit, one may](https://reader030.vdocument.in/reader030/viewer/2022040602/5e9b20117c38ad2a541939a4/html5/thumbnails/16.jpg)
Example
16
© A
hmad
El-B
anna
Ele
c. Ct
s A , L
ec#1
4 , F
all 2
016
• Calculate the voltage gain of the shown circuit.
![Page 17: Feedback Amplifiers 16bu.edu.eg/portal/uploads/Engineering, Shoubra...Feedback Amplifier •Depending on the relative polarity of the signal being fed back into a circuit, one may](https://reader030.vdocument.in/reader030/viewer/2022040602/5e9b20117c38ad2a541939a4/html5/thumbnails/17.jpg)
• For more details, refer to:
• Chapter 14 at Boylestad, Electronic Circuits and Devices,11th edition.
• The lecture is available online at:
• http://bu.edu.eg/staff/ahmad.elbanna-courses/11966
• For inquires, send to:
17
© A
hmad
El-B
anna
Ele
c. Ct
s A , L
ec#1
4 , F
all 2
016