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第八章 集成运放组成的负反馈 放大电路 |
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实现Y=3X1+2X2+X3的电路可以是反相加法器与反相器的串联，如图二（c）所示。 |
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令 Rf=100kΩ |
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取 Rf/R1=3,
Rf/R2=2,
Rf/R3=1,
Rb1=
R1//R2//R3//Rf,
Rb2=0.5R |
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即 |
R1=33.3kΩ,
R2=50kΩ,
R3=100kΩ，
Rb1=14.3kΩ |
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实现Y=2X1-X2的电路可以是减法器，参见图二（d）。 |
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根据减法器的运算关系 |
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由R2/R1=1 |
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则取R1=R2
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又有 |
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同时两输入端外电阻平衡条件为 |
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R3=
R1//R2=0.5R1,R4=
(开路）
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