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EE221 Electronics -II
Lecture
EE221 Spring 2012
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Electronics II: Feedback Concepts and Definitions, Slides of Electronics
IC design philosophy and comparison of MOSFET and BJT, basic MOS/BJT cell, IC biasing, transistor parings, BJT differential pair, operational amplifier, power amplifiers. Prof. Saleem Iftekhar delivered this lecture. Its main points are: Feedback, COncepts, Definition, Amplifiers, Transfer, Function, Characteristics, Ideal, Gain, Load
Typology: Slides
2011/2012
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1
EE221 Electronics -II
Lecture
EE221 Spring 2012
EE-221 ELECTRONICS -II
EE221 Spring 2012
2
Acknowledgement:
The author of these slides acknowledges that
most of the slides used in this course have been taken from thecourse material provided in the CD accompanying the two text booksmentioned below.
Some of the slides have been modified and some
new slides have been added.
The author would like to appreciate
and give full credit to the efforts of the original creator of the slidesand would
categorically mention that the material used is
purely for academic purpose and not whatsoever forcommercial use.No commercial use of these slides is either intended and allthose accessing this material are advised to use this materialonly for academic
non-commercial purpose.
^
Microelectronic Circuits Sixth Edition,
by Sedra, Smith Oxford University Press
^
Fundamentals of Microelectronics, by Behzad Razavi, John Wiley & Sons Inc ^
Microelectronics, Circuit Analysis & Design 3 Ed,
by Donald A Neamen McGraw Hill
Modified by Assistant Professor Saleem Iftekhar, SEECS NUST
RECALL: FB amplifier Gain
ↈ^
ⅱ ∆ⅵ
-^
is called >>>
OPEN LOOP GAIN
-^
is called >> >
FEEDBACK
FACTOR
-^
is called the >>>
LOOP GAIN.
-^
is called >>>
AMOUNT OF FEEDBACK
-^
ↈ^
is the called >>>
CLOSED LOOP GAIN
RECALL: FB amplifier Gain
ↈ^
ⅱ ∆ⅵ
-^
For positive
-^
ↈ^
is smaller than
-^
If
then
ↈ^
❸ ∶
The closed loop gainis totally dependenton
β
which is
normally composedof passive elements.
- Example 10.1 S&S 6Ed page
FB Amplifiers (Properties)
-^
GAIN DESENSITIVITY
-^
ↈ^
∆ ⅱ ∆ⅵ
⅗ ❸⡸⅗∶
-^
Differentiating Both sides we
ↆ⅗ ❸⡸⅗∶
❹
-^
Dividing (2) by (1) we get
〱。
㊁ 。㊁
⡩ ⡩⡸。め
ↆ⅗⅗
-^
is called De-sensitivity factor
Percentage changein
⅗
ↈ^
is smaller than
percentage in A by afactor
❸
⅗∶
FB Amplifier (Properties)
-^
BW EXTENSION
-^
⅗ Ⅹ
( ❸⡸ ⁄^
∁ ≙
Ⅴ ⁄^
)
❸⡸∶
(⅗
Ⅹ
( ❸⡸ ⁄^
∁ ≙
Ⅴ ⁄^
)^
OR we can rewrite as
-^
⅗ Ⅹ
( ❸⡸ ⁄^
⅗Ⅹ
∶ )
❸⡸∁ ≙
Ⅴ (❸⡸ ⁄^
⅗ Ⅹ
∶ )
-^
⅗ Ⅹↈ ❸⡸∁ ≙
Ⅴↈ ⁄
FB Amplifier (Properties)
-^
BW EXTENSION
-^
⅗ Ⅹↈ ❸⡸∁ ≙
Ⅴↈ ⁄
-^
Ⅹↈ
Ⅹ
⁄^
Ⅹ
-^
Ⅴↈ
Ⅴ^
Ⅹ
-^
Similarly it can be shown that for the lower cut-offfrequency^ ≙
Ⅸↈ
Ⅸ^
Ⅹ
FB Amplifier (Properties)
ↀ
↖
ↀ ⅵ^
ↀ ⅱ
=ⅱ
❸^
ⅵ^
↖
Signal-Noise -Ratio =
ⅵ ⅰ
ↀ
ⅵ ↀ ↖^ ⅵ ⅰ
⅗
ↀ❸
ⅵ ⅗❸
ↀ ↖
ↀ ⅵ ↀ ↖
FB Amplifier (Properties)
ⅱ
ⅵ^
↖^
❸^
Signal-Noise -Ratio =
ⅵ ⅰ
ↀ
ⅵ ↀ ↖
ⅵ ⅰ^
ↀ ⅵ ↀ ↖
ↀ
↖
ↀ ⅵ^
ↀ ⅱ
FB Amplifier (Properties)
ↀ ⅱ
ↀ
↖
ↀ
ⅵ^
ↀ ❹^
ↀ ❸
Signal-Noise -Ratio =
ⅵ ⅰ
ↀ
ⅵ ↀ ↖
=ⅱ
ⅵ^
❹^
❹
⁄^
↖^
❸^
❹
ⅱ
ⅵ^
⁄^
↖^
❹
⁄^
❹^
FB Amplifier (Properties)
Signal-Noise -Ratio =
ⅵ ⅰ
ↀ
ⅵ ↀ ↖
ⅱ
ⅵ^
⁄^
↖^
❹
⁄^
❹^
FB Amplifier (Properties)
Non Linear Distortion ( FB factor 0.01)
Gain 90.
Gain 50