分析仪器中常用到对数和反对数放大器。这两种放大器可由运算放大器辅以半导体二极管或三极管构成。不管是用二极管还是三极管作为非线性元件,其基本原理均是基于PN结的如下特性: I=I_s(c(QU/kT)-1)亦即: U=(kT/Q)ln(I/Is)式中:U为PN结的正相电压,I为正相电流;Q是电子的电荷量,等于1.602×10~(19) Analytical instruments commonly used to logarithmic and anti-logarithmic amplifier. Both amplifiers can be supplemented by op amps with semiconductor diodes or triodes. Whether diode or triode as a non-linear element, its basic principle is based on the following characteristics of PN junction: I = I_s (c (QU / kT) -1) That is: U = (kT / Q) ln Is) where: U is the PN junction of the normal phase voltage, I is the normal phase current; Q is the charge of the electron, equal to 1.602 × 10 ~ (19)