ELE533 Bipolar Devices
Final Exam

August 9, 2002


  1. Consider a silicon npn transistor with a base width of 1.0 micron, base doping, Na = 1017 acceptors/cm3, emitter doping, Nde = 5x1019 donors/cm3, emitter width is 1.5 microns, electron and hole life times are 10 -6 sec. in the emitter and 10 -9 sec. in the base, the emitter area is 20 microns by 40 microns.


    1. beta________________

    If the collector current is 1 mA, find:

    1. gm__________________

    2. rpi , the incremental base-emitter resistance_____________

    3. Cd, the base-emitter diffusion capacitance______________

    4. Assume the diffusion capacitance is much greater than the base emitter and base collector junction capacitances and find;
      FT, the frequency at which the magnitude of beta is one_______________