8310  基本对数放大器使用了跨导线性电路

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8310  基本对数放大器使用了跨导线性电路

对数放大器是一种特殊的放大器，其输出信号幅度与输入信号幅度呈对数函数关系。这种放大器主要用于将信号转换成其等效对数值，涉及一种非线性运算放大器。对数放大器在实际应用中兼具线性和对数放大功能。当输入信号较弱时，8310 表现为线性放大器，增益较大；而当输入信号较强时，它转变为对数放大器，增益随输入信号的增加而减小。

对数放大器在雷达设备中有特别重要的作用。它不仅可以保证雷达接收机有很宽的动态范围，而且可以限制接收机输出的杂波干扰电平，达到恒虚警的效果。此外，对于单脉冲雷达，对数放大器可以归一化角误差信号；对于动目标显示雷达，它还可以抑制固定目标起伏。

在IC设计中，基本对数放大器使用了跨导线性电路，因此也被称为跨导线性（Translinear）对数放大器。跨导线性电路是电流模电路的主要组成部分，也是许多线性和非线性模拟集成电路的理论基础。跨导线性对数放大器基于双极性三极管（BJT）的对数特性。理想情况下，BJT的基极-发射极电压（UBE）与其基极电流（ic）之间呈对数关系。

此外，8310 当处理输入信号幅度变化很大的情况时，如连续信号或接近连续的信号（如AM、单边带调制信号等），对数放大器也表现出其优势。在这种情况下，自动增益控制（AGC）系统或限幅放大器可能无法有效处理，而对数放大器则能够解决此问题。

8310  基本对数放大器使用了跨导线性电路

A logarithmic amplifier is a special amplifier whose output signal amplitude is a logarithmic function of the input signal amplitude. This amplifier is mainly used to convert a signal into its equivalent pair value and relates to a nonlinear operational amplifier. Logarithmic amplifiers have both linear and logarithmic amplifiers in practical applications. When the input signal is weak, the 8310 behaves as a linear amplifier with large gain. When the input signal is strong, it turns into a logarithmic amplifier, and the gain decreases as the input signal increases.

Logarithmic amplifiers play a particularly important role in radar equipment. It can not only ensure that the radar receiver has a wide dynamic range, but also limit the clutter interference level of the receiver output to achieve the effect of constant false alarm. In addition, for monopulse radar, the logarithmic amplifier can normalize the angular error signal; For moving target display radar, it can also suppress fixed target fluctuation.

In IC design, basic logarithmic amplifiers use Translinear circuits and are therefore also known as translinear logarithmic amplifiers. Transconductor circuit is the main component of current mode circuit, and also the theoretical basis of many linear and nonlinear analog integrated circuits. Transwire logarithmic amplifiers are based on the logarithmic characteristics of bipolar triode (BJT). Ideally, a BJT has a logarithmic relationship between its base-emitter voltage (UBE) and its base current (ic).

In addition, the 8310 also shows its advantages when dealing with situations where the amplitude of the input signal varies greatly, such as continuous signals or near-continuous signals (such as AM, single sideband modulated signals, etc.). In such cases, an automatic gain control (AGC) system or a limiting amplifier may not be able to handle this effectively, while a logarithmic amplifier is able to solve this problem.