数字晶体管f_T测试误差分析

Deviation Analysis of Digital Transistor f_T Test

特征频率fT是数字晶体管的一项重要参数。文章叙述了普通晶体管特征频率fT的测试原理,并从模拟数字晶体管的等效电路着手,通过理论推导,深入分析了fT产生测试误差甚至无法测量的原因。指出基极串联电阻的接入破坏了基极注入信号必须是恒流的测试条件;基极-发射极并联电阻的接入对测试信号起到了分流作用。在这两方面共同作用下,经被测管放大后的集电极信号减小,导致增益下降,必然会产生很大的测试误差。同时文中进行了一系列的试验,与分析结果相符合,并分别给出了串联电阻和并联电阻对fT影响程度的具体数据及曲线图,可为数字晶体管的生产厂商和使用单位的有关人员提供帮助,也可供测试仪器制造厂家的研发人员作为参考。

Characteristic frequency fT is an important parameter of digital transistors.This paper formulates the testing principle of transistor’s characteristic frequency fT.Through theoretical derivation for the equivalent circuit of analog digital transistors,the authors deeply analyze the reason of the fT testing error which even may not be measured.This paper indicates that the connection of base series resistance would destroy the testing condition that base injected signal must be constant current.The connection of baseemitter parallel resistance has a shunting effect on the testing signal.Under effect of two aspects,collector signal after the amplification of the measured tube will decrease,which resulting in gain goes down.And serious testing error will occur inevitable.Meanwhile the authors have made a series of experiments;the result is consistent with analysis result.In this paper,specific data and the curve chart are given,which show influence that series resistance and parallel resistance make on fT.This paper can help relative persons from manufacturer of digital transistors,and manufacturing factory,and can be referenced by researcher from factories of testing equipment.