Transient Analysis Of Minority-Carrier Diffusion In The Base Of P/N Junction Diodes And Bipolar-Transistors

The time-dependent minority carrier distribution in the base of a bipolar p/n junction subjected to a step-up or step-down (switch-on or switch-off) applied voltage has been obtained. Analytical expressions are found by solving the time-dependent minority-carrier diffusion equation with appropriate boundary conditions. A general case with arbitrary base width under both switch-on and switch-off transients is considered. In addition, the validity of the constant-voltage and constant-current approaches under different base widths and different bias conditions are also discussed. This analytical approach is also applied to obtain the turn-on current transients of a forward-active bipolar transistor. The results are compared with those simulated from the conventional Gummel-Poon model and obtained from measurement