A Study of a.c. Capacitance of Bipolar Devices

• Main Authors: Chyau Chwan-Gwo, 喬傳國
• Other Authors: Jang Sheng-Lyang
• Format: Others
• Language: zh-TW
• Published: 1994
• Online Access: http://ndltd.ncl.edu.tw/handle/49255459667835611497

碩士 === 國立臺灣科技大學 === 工程技術研究所 === 82 === A theortical study of a.c. capacitance of bipolar devices, such as p-n junction diode and bipolar junction transistor, has been made. Firstly, we present a theory for the voltage distribution of the applied voltage across a p-n junction diode. In the theory , we allow for the voltage drops formed by the gradient ofmajority carrier concentration and quasi-Fermi levels in quasi- neutral region, According to the theory, we derive new d. c. and a.c. equivalent circuits for p-n junction diode, by which we can calculate device characteristics at any injection level, Secondly , we extend the diode theory to bipolar junction transistor and investigate the d.c. current-voltage characteristics and the a.c. capacitance of emitter-base junction of a BJT worked at forward active region, We find that the a.c. capacitance increases withincreasing bisa initially, and then drcreases to negative value. The simulation results are qualitatively similar to those of experiments.