Bilingual edition: English is preserved and Chinese follows each unit. Terminology uses the confirmed v20260916 glossary; automated semantic review remains traceable.
中英双语版：英文原文完整保留，中文紧随对应单元；术语采用 v20260916 确认表，自动语义审校结果可追溯。

Practical Benefits:Negative Feedback

实用效益：负反馈

Most practical amplifier circuits use negative feedback for the following practical benefits:

大多数实用放大电路都采用负反馈，因为有以下实际好处：
Stabilization of voltage gain
电压增益的稳定
Decreasing output impedance
降低输出阻抗
Increasing input impedance
增加输入阻抗
Decreasing distortion
畸变减小
Increasing bandwidth
增加带宽
Index

Electronics concepts

Op-amp concepts

Feedback concepts
索引 电子概念 运算放大器概念 反馈概念
 
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Stabilization of Voltage Gain

电压增益的稳定

One of the benefits of negative feedback is the stabilization of the voltage gain of an amplifier against changes in the components (e.g., with temperature, frequency, etc. ). If you represent the gain without feedback (the open loop gain) by A0 , then the system gain with negative feedback is

负反馈的一个好处是使放大器的电压增益对元件变化（例如温度、频率等）具有稳定性。如果用没有反馈的增益（开环增益）表示为 A₀ ，则带有负反馈的系统增益为

where B is the fraction of the output which feeds back as a negative voltage at the input. The extent of this stabilizing influence can be illustrated as follows:

其中，B 表示输出中反馈到输入端作为负电压的比例。这种稳定作用的程度可以如下方式来说明：
This stabilization increases the effective bandwidth.
这种稳定措施增加了有效带宽。
Why use negative feedback?
为何使用负反馈？
 Index

Electronics concepts

Op-amp concepts

Feedback concepts
索引 电子概念 运算放大器概念 反馈概念
 
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Increasing Input Impedance

增加输入阻抗
The input impedance is
输入阻抗是
 which without negative feedback is Zin0 .
没有负反馈时，阻抗为Z in0。
But with feedback, the current is reduced to
但带有反馈时，电流会降低到
Why use negative feedback?
为何使用负反馈？
 Index

Electronics concepts

Feedback concepts

Reference
Simpson
Sec 7.2
索引 电子概念 反馈概念 参考 斯impson 第7章第2节
 
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Decreasing Output Impedance

降低输出阻抗

As in the approach to input impedance, the effect of negative feedback on output impedance can be obtained by analysis of the equivalent circuit.

Things become more subtle here because the input voltage vin must be held constant while we see how vout varies with iout . The easiest way to do this is with the partial derivative
Why use negative feedback?
为何使用负反馈？
正如输入阻抗的处理方式一样，可以通过等效电路的分析来获得负反馈对输出阻抗的影响。这里情况变得更加微妙，因为必须在保持输入电压v in不变的情况下，观察v out随i out的变化。最简单的方法就是使用偏导数。
 Index

Electronics concepts

Feedback concepts

Reference
Simpson
Sec 7.2
索引 电子概念 反馈概念 参考 斯impson 第7章第2节
 
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