发射极电流集边效应理论的SPICE模拟验证

Verification on Theory of Edge\|Crowding\|Effect of Emitter Current with SPICE Simulation\+*

发射极电流集边效应是由晶体管基极电阻的自偏压引起的 ,描述该效应的微分方程早已建立 ,这里设计了一种用 SPICE验证精确解 /近似解的新方法 .结果表明 :近似解是在 V( x) VT 的前提条件下求得的 ,仅在弱注入区和中等注入区适用 ,不能给出在强注入区和极强注入区的归一化电位和电流密度的分布函数 ;相反 ,基于精确解的理论却能给出从弱注入区到极强注入区的归一化电位和电流密度的分布函数 ,且与用 SPICE模拟得到的结果吻合 .结论是 :从整体来看 ,精确解的理论比近似解的理论描述该效应要稍好一些 ,因为前者的适用范围比后者宽 .应当强调指出 。

The edge\|crowding\|effect of emitter current is due to the self\|bias of base resistor in a transistor.The differential equation describing the effect has already been set up,with the approximate solution being found,while the precise solution also been solved by separation of variables.A new method is presented to verify the precise/approximate solutions by SPICE simulation.The result shows that the approximate solution is obtained under the condition of V(x)V\- T,so it applies only in the range from weak injection to moderate injection,i.e.it is impossible to give the distribution of normalised voltage and current density in the range from strong injection to super\|strong injection.On the contrary,on the basis of precise solutions theory it is possible to do so in the whole range,from weak injection to super\|strong injection,which are coincident with the result of SPICE simulation.A conclusion is drawn that the theory of precise solution is better than the approximate one in describing the effects because the suitable range the former is wider than that of the latter.It should be emphasised that the effect occurs mainly in the range from strong injection to super\|strong injection.