The base emitter BJT

Discussion in 'Homework Help' started by u-will-neva-no, Apr 25, 2011.

  1. u-will-neva-no

    Thread Starter Member

    Mar 22, 2011
    230
    2
    Hello everyone, my aim is to derive an expression for the small signal resistance, rπ, using the equation Ib = Io (exp(ηVbe/Vt)-1).

    I have no idea where to start...could someone please link me to a relevant website or head me in the right direction? Much appreciated as always!
     
  2. t_n_k

    AAC Fanatic!

    Mar 6, 2009
    5,448
    782
    Take the derivative of Ib with respect to Vbe, which equates to the small signal conductance [gπ] - the inverse of the small signal resistance [per your notation rπ=1/gπ].

    It is more common to derive the dynamic emitter resistance 're' which is routinely used in small signal BJT amplifier analysis.

    Look up Shockley diode equation.
     
    u-will-neva-no likes this.
  3. u-will-neva-no

    Thread Starter Member

    Mar 22, 2011
    230
    2
    Brilliant, thankyou!
     
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