Consider a BJT amplifier in bypawed commonemitter configurat

Consider a BJT amplifier in by-pawed common-emitter configuration operating with a collector current bias, I_C. Assume that the net collector load is R_O = R_C||R_L The input potential at the base is v_b Draw a weakly non-linear equivalent circuit for the BJT amplifier with input v_b and output v_o. Derive expressions for the Taylor Series coefficients (up to third order) in terms of the product V_M = I_C R_O and the emitter junction thermal potential, V_T. Assume the current gain is high enough that I_E = I_C. Note that a_1 = -di_E/dv_BE R_O = -d/dv_BE I_E e^v_BE/V_T R_O = -V_M d/dv_BE e^v_BE/V_T, and a_2 = -1/2 d^2 i_E/dv_BE^2 R_O, etc.

Solution

2. vo/vb = Ro//Ri

R0= Rc//Rl

3. I = Io e^V/nVt

^{Vt = T/14600 v}

n=1 for silicon

n=2 for germanium