JFET构成的运算放大器输入过压保护电路设计

Design of Input Overvoltage Protection Circuit of Operational Amplifier Composed of JFET

为弥补传统运算放大器输入过压保护电路中电阻加钳位二极管结构的缺陷,设计一种新型输入过压保护电路。电路采用中科渝芯4μm双极工艺完成设计,主要由结型场效应管器件JFET以及钳位二极管构成,利用JFET沟道夹断原理使过压电流最终趋于饱和,实现过压保护功能。采用对称性设计,使正负过压下饱和过压电流相等。经仿真实验,结果表明此款运算放大器的输入过压保护电路相较传统结构噪声更小,对过压电流具有更强的限制作用,具有一定的应用价值。

In order to make up for the defects of the traditional input overvoltage protection circuit of operational amplifier,a new input overvoltage protection circuit is designed.The circuit is designed by Analog Foundries's 4μm bipolar process,which is mainly composed of JFET and clamping diode.The overvoltage current is finally saturated by using the principle of JFET channel pinch-off,and the overvol-tage protection function is realized.Symmetry design is adopted to make the saturation overvoltage current equal under positive and negative overvoltage.The simulation results show that the input overvoltage protection circuit of the operational amplifier has less noise than the traditional structure,has a stronger limiting effect on overvoltage current,and has certain application value.