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本文叙述了一个具有高准确度的对数函数和通带较宽的对数放大器。该放大器用RC充放电的指数函数和脉宽调制的方法,提高了对数函数的准确度,从而可以解决天文、宇航、精确测量和通信等方面的很多关键问题。 根据RC充放电电压与时间的指数关系,再将时间用脉冲调制转换成电压,就构成了输入输出的对数关系。使用“取样定理”、“香农基础信道容量公式”和“多级放大带宽公式”等,对该系统进行了理论分析。搭试了一个具体电路,取得了系统特性数据,证实了该系统的对数函数准确度可达99％以上。
This article describes a logarithmic function with high accuracy and a wide logarithmic amplifier with a wide passband. The amplifier uses RC exponential function and pulse width modulation method to improve the accuracy of logarithm function so as to solve many key problems in astronomy, astronautics, precise measurement and communication. According to the exponential relationship between RC charge and discharge voltage and time, and then the time pulse modulation into voltage, constitute the logarithmic relationship between input and output. Using “sampling theorem”, “Shannon basic channel capacity formula” and “multi-stage amplification bandwidth formula”, the system is analyzed theoretically. Took a specific circuit, obtained the system characteristic data, confirmed that the system logarithmic function accuracy may reach above 99%.