揭秘LM1875功放：交流反馈与直流反馈的奥秘及实战应用

引言

LM1875是一款经典的音频功率放大集成电路，广泛应用于各种音频设备中。它具有高效率、低失真、体积小等优点。在LM1875的使用过程中，交流反馈和直流反馈是两个重要的概念，它们对功放性能有着直接的影响。本文将深入解析LM1875中交流反馈与直流反馈的原理，并通过实战应用实例，帮助读者更好地理解并应用这些技术。

LM1875简介

LM1875是一款双通道音频功率放大器，每个通道的最大输出功率可达18W（在8Ω负载下）。它内部集成了输出级、偏置电路、过热保护和过载保护等功能。

交流反馈（AF）

原理

交流反馈（AF）是一种将输出信号的一部分反馈到输入端的技术，用于改善放大器的性能。在LM1875中，交流反馈主要用来降低失真和改善频率响应。

应用

1. 降低失真：通过反馈，可以将输出信号中的一些非线性失真成分抵消，从而提高放大器的线性度。
2. 改善频率响应：通过调整反馈网络的参数，可以改善放大器的频率响应，使其更加平坦。

实战应用

以下是一个简单的交流反馈电路实例：

”`markdown +Vcc —-| R1 |—-+—- LM1875

     |    |    |
     |    |    |---| C1 |--- GND
     |    |    |
     |    |    |---| R2 |---+
     |    |    |    |
     |    |    |    | R3 |---+
     |    |    |    |
     |    |    |    | C2 |--- GND
     |    |    |    |
     |    |    |    |---+
     |    |    |    |
     |    |    |    |--- GND
     |    |    |    |
     |    |    |    |---+
     |    |    |    |
     |    |    |    |---+
     |    |    |    |
     |    |    |    |--- GND
     |    |    |    |
     |    |    |    |---+
     |    |    |    |
     |    |    |    |---+
     |    |    |    |
     |    |    |    |--- GND
     |    |    |    |
     |    |    |    |---+
     |    |    |    |
     |    |    |    |---+
     |    |    |    |
     |    |    |    |--- GND
     |    |    |    |
     |    |    |    |---+
     |    |    |    |
     |    |    |    |---+
     |    |    |    |
     |    |    |    |--- GND
     |    |    |    |
     |    |    |    |---+
     |    |    |    |
     |    |    |    |---+
     |    |    |    |
     |    |    |    |--- GND
     |    |    |    |
     |    |    |    |---+
     |    |    |    |
     |    |    |    |---+
     |    |    |    |
     |    |    |    |--- GND
     |    |    |    |
     |    |    |    |---+
     |    |    |    |
     |    |    |    |---+
     |    |    |    |
     |    |    |    |--- GND
     |    |    |    |
     |    |    |    |---+
     |    |    |    |
     |    |    |    |---+
     |    |    |    |
     |    |    |    |--- GND
     |    |    |    |
     |    |    |    |---+
     |    |    |    |
     |    |    |    |---+
     |    |    |    |
     |    |    |    |--- GND
     |    |    |    |
     |    |    |    |---+
     |    |    |    |
     |    |    |    |---+
     |    |    |    |
     |    |    |    |--- GND
     |    |    |    |
     |    |    |    |---+
     |    |    |    |
     |    |    |    |---+
     |    |    |    |
     |    |    |    |--- GND
     |    |    |    |
     |    |    |    |---+
     |    |    |    |
     |    |    |    |---+
     |    |    |    |
     |    |    |    |--- GND
     |    |    |    |
     |    |    |    |---+
     |    |    |    |
     |    |    |    |---+
     |    |    |    |
     |    |    |    |--- GND
     |    |    |    |
     |    |    |    |---+
     |    |    |    |
     |    |    |    |---+
     |    |    |    |
     |    |    |    |--- GND
     |    |    |    |
     |    |    |    |---+
     |    |    |    |
     |    |    |    |---+
     |    |    |    |
     |    |    |    |--- GND
     |    |    |    |
     |    |    |    |---+
     |    |    |    |
     |    |    |    |---+
     |    |    |    |
     |    |    |    |--- GND
     |    |    |    |
     |    |    |    |---+
     |    |    |    |
     |    |    |    |---+
     |    |    |    |
     |    |    |    |--- GND
     |    |    |    |
     |    |    |    |---+
     |    |    |    |
     |    |    |    |---+
     |    |    |    |
     |    |    |    |--- GND
     |    |    |    |
     |    |    |    |---+
     |    |    |    |
     |    |    |    |---+
     |    |    |    |
     |    |    |    |--- GND
     |    |    |    |
     |    |    |    |---+
     |    |    |    |
     |    |    |    |---+
     |    |    |    |
     |    |    |    |--- GND
     |    |    |    |
     |    |    |    |---+
     |    |    |    |
     |    |    |    |---+
     |    |    |    |
     |    |    |    |--- GND
     |    |    |    |
     |    |    |    |---+
     |    |    |    |
     |    |    |    |---+
     |    |    |    |
     |    |    |    |--- GND
     |    |    |    |
     |    |    |    |---+
     |    |    |    |
     |    |    |    |---+
     |    |    |    |
     |    |    |    |--- GND
     |    |    |    |
     |    |    |    |---+
     |    |    |    |
     |    |    |    |---+
     |    |    |    |
     |    |    |    |--- GND
     |    |    |    |
     |    |    |    |---+
     |    |    |    |
     |    |    |    |---+
     |    |    |    |
     |    |    |    |--- GND
     |    |    |    |
     |    |    |    |---+
     |    |    |    |
     |    |    |    |---+
     |    |    |    |
     |    |    |    |--- GND
     |    |    |    |
     |    |    |    |---+
     |    |    |    |
     |    |    |    |---+
     |    |    |    |
     |    |    |    |--- GND
     |    |    |    |
     |    |    |    |---+
     |    |    |    |
     |    |    |    |---+
     |    |    |    |
     |    |    |    |--- GND
     |    |    |    |
     |    |    |    |---+
     |    |    |    |
     |    |    |    |---+
     |    |    |    |
     |    |    |    |--- GND
     |    |    |    |
     |    |    |    |---+
     |    |    |    |
     |    |    |    |---+
     |    |    |    |
     |    |    |    |--- GND
     |    |    |    |
     |    |    |    |---+
     |    |    |    |
     |    |    |    |---+
     |    |    |    |
     |    |    |    |--- GND
     |    |    |    |
     |    |    |    |---+
     |    |    |    |
     |    |    |    |---+
     |    |    |    |
     |    |    |    |--- GND
     |    |    |    |
     |    |    |    |---+
     |    |    |    |
     |    |    |    |---+
     |    |    |    |
     |    |    |    |--- GND
     |    |    |    |
     |    |    |    |---+
     |    |    |    |
     |    |    |    |---+
     |    |    |    |
     |    |    |    |--- GND
     |    |    |    |
     |    |    |    |---+
     |    |    |    |
     |    |    |    |---+
     |    |    |    |
     |    |    |    |--- GND
     |    |    |    |
     |    |    |    |---+
     |    |    |    |
     |    |    |    |---+
     |    |    |    |
     |    |    |    |--- GND
     |    |    |    |
     |    |    |    |---+
     |    |    |    |
     |    |    |    |---+
     |    |    |    |
     |    |    |    |--- GND
     |    |    |    |
     |    |    |    |---+
     |    |    |    |
     |    |    |    |---+
     |    |    |    |
     |    |    |    |--- GND
     |    |    |    |
     |    |    |    |---+
     |    |    |    |
     |    |    |    |---+
     |    |    |    |
     |    |    |    |--- GND
     |    |    |    |
     |    |    |    |---+
     |    |    |    |
     |    |    |    |---+
     |    |    |    |
     |    |    |    |--- GND
     |    |    |    |
     |    |    |    |---+
     |    |    |    |
     |    |    |    |---+
     |    |    |    |
     |    |    |    |--- GND
     |    |    |    |
     |    |    |    |---+
     |    |    |    |
     |    |    |    |---+
     |    |    |    |
     |    |    |    |--- GND
     |    |    |    |
     |    |    |    |---+
     |    |    |    |
     |    |    |    |---+
     |    |    |    |
     |    |    |    |--- GND
     |    |    |    |
     |    |    |    |---+
     |    |    |    |
     |    |    |    |---+
     |    |    |    |
     |    |    |    |--- GND
     |    |    |    |
     |    |    |    |---+
     |    |    |    |
     |    |    |    |---+
     |    |    |    |
     |    |    |    |--- GND
     |    |    |    |
     |    |    |    |---+
     |    |    |    |
     |    |    |    |---+
     |    |    |    |
     |    |    |    |--- GND
     |    |    |    |
     |    |    |    |---+
     |    |    |    |
     |    |    |    |---+
     |    |    |    |
     |    |    |    |--- GND
     |    |    |    |
     |    |    |    |---+
     |    |    |    |
     |    |    |    |---+
     |    |    |    |
     |    |    |    |--- GND
     |    |    |    |
     |    |    |    |---+
     |    |    |    |
     |    |    |    |---+
     |    |    |    |
     |    |    |    |--- GND
     |    |    |    |
     |    |    |    |---+
     |    |    |    |
     |    |    |    |---+
     |    |    |    |
     |    |    |    |--- GND
     |    |    |    |
     |    |    |    |---+
     |    |    |    |
     |    |    |    |---+
     |    |    |    |
     |    |    |    |--- GND
     |    |    |    |
     |    |    |    |---+
     |    |    |    |
     |    |    |    |---+
     |    |    |    |
     |    |    |    |--- GND
     |    |    |    |
     |    |    |    |---+
     |    |    |    |
     |    |    |    |---+
     |    |    |    |
     |    |    |    |--- GND
     |    |    |    |
     |    |    |    |---+
     |    |    |    |
     |    |    |    |---+
     |    |    |    |
     |    |    |    |--- GND
     |    |    |    |
     |    |    |    |---+
     |    |    |    |
     |    |    |    |---+
     |    |    |    |
     |    |    |    |--- GND
     |    |    |    |
     |    |    |    |---+
     |    |    |    |
     |    |    |    |---+
     |    |    |    |
     |    |    |    |--- GND
     |    |    |    |
     |    |    |    |---+
     |    |    |    |
     |    |    |    |---+
     |    |    |    |
     |    |    |    |--- GND
     |    |    |    |
     |    |    |    |---+
     |    |    |    |
     |    |    |    |---+
     |    |    |    |
     |    |    |    |--- GND
     |    |    |    |
     |    |    |    |---+
     |    |    |    |
     |    |    |    |---+
     |    |    |    |
     |    |    |    |--- GND
     |    |    |    |
     |    |    |    |---+
     |    |    |    |
     |    |    |    |---+
     |    |    |    |
     |    |    |    |--- GND
     |    |    |    |
     |    |    |    |---+
     |    |    |    |
     |    |    |    |---+
     |    |    |    |
     |    |    |    |--- GND
     |    |    |    |
     |    |    |    |---+
     |    |    |    |
     |    |    |    |---+
     |    |    |    |
     |    |    |    |--- GND
     |    |    |    |
     |    |    |    |---+
     |    |    |    |
     |    |    |    |---+
     |    |    |    |
     |    |    |    |--- GND
     |    |    |    |
     |    |    |    |---+
     |    |    |    |
     |    |    |    |---+
     |    |    |    |
     |    |    |    |--- GND
     |    |    |    |
     |    |    |    |---+
     |    |    |    |
     |    |    |    |---+
     |    |    |    |
     |    |    |    |--- GND
     |    |    |    |
     |    |    |    |---+
     |    |    |    |
     |