ELE533 Bipolar Devices
Final Exam

August 13, 1998

Question 1

NAME___________________________________________________________

Consider a silicon npn transistor with a base width of 1.0 micron, base doping, Na = 1017 acceptors/cm3, emitter doping, Nde = 5x1018 donors/cm3, emitter width is 1.5 microns, electron and hole life times are 10-6 sec, the emitter area is 20 microns by 50 microns.

Find:

  • the emitter injection efficiency________________

  • beta________________

    •  If the collector current is 1 mA, find:

  • gm__________________

  • rb, the incremental base input resistance_____________

  • Cd, the base emitter diffusion capacitance______________

  • 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_______________

    •