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!

 

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.

 

Brilliant, thankyou!