Calculating fmax of bjt. (cjc from doping levels ?)

Discussion in 'Homework Help' started by mikey20, Dec 17, 2012.

  1. mikey20

    Thread Starter New Member

    Dec 17, 2012
    Hi. Could you help me with one problem that seemed too difficult for me?
    Given that Nd=10^16/cm^-3 , Na=10^14/cm^-3 , β(ω=300MHz)=60, Vcb=10 V, rbb=20 ohms,
    calculate the ωmax (fmax ?) of a bjt ?
    I am struggling to find a proper equation to obtain Cjc from Nd and Vcb, but i'm not even sure if it's possible.
    the other problem : find differential conductance of a pn junction, given that I=50mA , electron lifespan: 1us. Does the electron lifespan change anything or influence the diff. conductance ? thanks in advance