对数放大器在通信、医疗、军事和工业等领域有着广泛的应用，它的作用是把大动态范围的信号转化为小动态范围的信号以便后续的处理。在本文中，介绍了对数放大器的分类、原理和应用，并利用正向偏置pn结的I-V对数关系，在Cadence环境下，完成了一个集成直流对数放大器的前端设计。设计的对数放大器，基于上华0.5混合信号工艺模型。电源为 ，输入信号为电流形式，动态输入范围为100pA～1mA（140dB），对数一致性误差小于1%，工作温度范围为（-10℃～70℃）。
关键词：对数放大器 ，对数转化器.
A design of integrated logarithmic amplifier
with 100dB dynamic range and high precision
Abstract
Logarithmic amplifier is widely used in communications, medical, military, and industrial systems . It's function is to convert input signals with wide dynamic range into output signals with small dymamic range to facilitate the follow-up treatment.
This paper describes the classification, principles and applications of logrithmic amplifiers, and makes use of the logarithmic relationship between the voltage and current of a forward-biased PN junction, completed a front end design of a integrated DC logarithmic amplifier in Cadence IC design enviroment. The design is based on CSMC 0.5 mix process model, supplied by power. The form of input signal is current. The dynamic range of input signal is 100pA~1mA.(140dB). Log conformity error of full scale is less than 1%. The operation temperature range of this converter is –10℃~70℃.
Key words : logarithmic amplifier, logarithmic converter.
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