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电 子 技 术 PowerPoint PPT Presentation


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电 子 技 术. 欢迎各位光临指导. 执教者:谢婷. 第四章 放大电路中的反馈. 基本概念及判别方法 负反馈放大电路组态. 练习. 定义:将放大电路的输出量 X 0 (U 0 或 I 0 ), 通过一定的方式传送到放大电路的输入回路来. 反馈. 净输入量。 它是 Xi 和 X f 的共同作用结果. 输入量 Xi. Xi ’. 输出量 Xo. . 放大电路. 反馈. 反馈量 X f. 正反馈与负反馈. 引入反馈后产生结果: 正反馈 : 使输出量的变化增大 负反馈 : 使输出量的变化减小 从引入反馈后净输入量的变化:

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电 子 技 术

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3827404


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X0(U0I0),.

XiXf

Xi

Xi

Xo

Xf


3827404

:

:

:

:


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:,


3827404

:

  • ,,,,,,

  • Xi=Xi+Xf

  • Xi=Xi-Xf


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Ui=Ui- Uf

Ui=Ui+ Uf

-

+

-

+

Uf

Uf

-

+


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Ii=Ii- If

If

_

Ii

Ii

+


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Ui

C


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//

R2R3


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;;

R2C


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R1b1T1c1b2T2c2

e2R3b1


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1

  • ,


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2

Ii

Ii

+

+

Ui

-

If

Ui

+

Uf

-

-


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  • Xi=Xi+Xf

  • Ui=Ui+Uf

  • Ii=Ii+If


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  • Uo=0Uf=0

  • Uo=0Uf0


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Ui=Ui+Uf

Uo=0

Uf=0


3827404

Ii=Ii+If

Uo=0

If=0


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Ui=Ui+Uf

Uo=0

Uf


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Ii=Ii+If

If


3827404

4-1


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48XiXo;Xi=Xi+Xf


A x o x i

AXoXi


A x o x i 4 1

A=Xo/Xi (4.1)


F x f x o

FXfXo


F x f x o 4 2

F=Xf/Xo (4.2)

AfXoXi


A f x o x i 4 3

Af=Xo/Xi (4.3)


4 1 4 2 x o ax i x f fx o f ax i x i x i x f 1 af x i a f

4.1) (4.2)Xo=AXi,Xf=Fxo=FAXiXi=Xi+Xf=1+AFXiAf


A f a 1 af 4 4

Af=A/1+AF (4.4)


Af 0 a f 1 1 af a f

AF0Af1/1+AFAf


X i x o 4 2

XiXo4.2


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Af--


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4 4 af 1

4.4AF>>1


A f 1 f 4 5

Af=1/F (4.5)


Af 1 4 5 a f a f

AF>>1(4.5)AfAf


4 2 4 3 4 5

(4.2)(4.3)(4.5)


X o x i x o x f

Xo/Xi~~Xo/Xf


X i x f 4 6

Xi~~Xf4.6)


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U i u f u i 0 i i i f i i 0

Ui~~UfUi~~0Ii~~IfIi~~0


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Af=Xo/Xi~~1/FAfXo~~1/FXiXoXiXXUiUo~~I/FUiIiUo~~I/FIiUiIo~~I/FUiIo~~I/FIiFXoXi


3827404

F


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4 7 a

4-7(a)


F u f u o r 1 r 1 r 2 4 7

F=Uf/Uo=R1/R1+R2 (4.7)


4 7 b

4-7(b)


I r2 u u o r 2 4 7

IR2=U--Uo/R2 (4.7)


I f u o u 0 r 2

IfUoU-=0R2


I f u o r 2

If=-Uo/R2


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F i f u o 1 r 2 4 8

F=If/Uo=-1/R2 (4.8)


4 7 c

4-7(c)


U f io r 1

Uf=IoR1


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F u f i o r 1 4 9

F=Uf/Io=R1 (4.9)


4 7 d u 0

4-7(d)U-=0


I f r 3 r 2 r 3 i o

If=-R3/R2+R3Io


I f i o f

IfIoF


F i f i o r 3 r 2 r 3 4 10

F=If/Io=-R3/(R2+R3) (4.10)


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Auf 4 7 a ui uf

AUF4-7AUI~~UF


Auf uo ui uo uf 1 f 4 11

AUF=UO/UI~~UO/UF=1/F 4.11


4 7 auf 1 r2 r1

4.7)AUF=1+R2/R1


4 7 b ii if ii 0 ui r1

4-7BII~~IFII~~0UIR1


Auf u0 ui u0 iir1 u0 ifr1 1 f 1 r 4 12

AUF=U0/UI~~U0/IIR1~~U0/IFR1=1/F1/R 4.12)


4 8 arf r2 r1

(4.8),ARF=-R2/R1


R1 rs ui us ausf

R1RSUIUSAUSF


Ausf 1 f 1 rs 4 13

AUSF~~1/F1/RS 4. 13


4 7 c ui uf

4-7CUI~~UF


Auf u0 ui i0rl uf 1 f rl 4 14

AUF=U0/UI~~I0RL/UF=1/FRL 4.14)


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