2-2 Electronic Feedback Systems
Blackboard 2.1
Blackboard 2.2
Viewgraph 2.1
V y,,, y,,,
Feedback system illustrating effects of disturbances y,
V
0

Effects Of Feedback on Noise and Nonlinearities 2-3
V,
V/ d
V2
Yd2 rJ d e
Open-loop system illustrating effects of disturbances
1 + a
2fI
Attenuator
Viewgraph 2.2
V0
Viewgraph 2.3
System
-8
Slope = 0.1
-3 -1
1 38
-2
-2.5
Transfer characteristics of the nonlinear element.
VA
Viewgraph 2.4

2-4 Electronic Feedback Systems
Viewgraph 2.5
vI
<-0.258
- 0.258
-
-0.203
10
3
10-3
0.203
0.258
> 0.258
Values of Variables at Breakpoints vE vI "F v,+0.250
-
-0.008
-0.003
10-3
10-3
0.003
0.008
v, - 0.250
vA =110E
103v
+250
-8
-3
-1
1
3
8
103'v - 250 vB= v0
-2.5
-
-2
2.5
0
0
2
2.5
2.5
vF=0.1v
-0.25
-0.25
-0.2
0
0
0.2
0.25
0.25
Viewgraph 2.6 t
Slope = 9.1
Slop e = 9.9
-0.258
-0.203
0
.
2 0 3 i
0.258
-10~3
10-3
System transfer characteristics
(closed loop) (Not to scale )
Slope = 0
,(
V -

Effects Of Feedback on Noise and Nonlinearities 2-5
Demonstration Photograph 2.1
Nonlinear amplifier demonstration
Much of our effort in this subject involves the properties of linear feedback control systems. However, feedback is often used to either provide controlled nonlinearities or to moderate the effects of the nonlinearities associated with virtually all physical components.
The economic impact of improving the performance of a nonlinear power handling element by adding gain at a low signal power level of the system can be substantial.
Similarly, feedback often provides a convenient and economical means for reducing the sensitivity of systems to externally applied disturbances.
Comments

2-6 Electronic Feedback Systems
Reading
Problems
Textbook: The material in this lecture parallels that in Sections
2.3.2 and 2.3.4. Please read this material if you have not done so in connection with Lecture 1.
Problem 2.1 (P2.3)
Problem 2.2 (P2.4)
Problem 2.3 (P2.5): For parts (a) and (b) assume that the sinusoidal disturbance term vN is equal to zero. Then, for part (c) let vN equal the indicated value of sin 377t.

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RES.6-010 Electronic Feedback Systems
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