Ⅰ所谓对数式的伏特计或对数式放大器是指这样的一种装置:它的输出电流或电压是与其输入讯号电压的对数成正比的。这样一种对数特性,使接在输出端的指示仪表能够以分贝为单位作出直线性的分度,因而其应用范围是很广的。此外这类装置在计算技术中也占有一定地位。有好几种方法获得这样的一种对数响应特性。其中最简单而有效的一种方法,是 The so-called logarithmic voltmeter or logarithmic amplifier refers to a device whose output current or voltage is proportional to the logarithm of its input signal voltage. Such a logarithmic characteristic, so that the indicator connected to the output can be measured in decibels linear scale, so its application is very wide. In addition, such devices also play a role in computing technology. There are several ways to achieve such a logarithmic response. One of the simplest and most effective ways is