V_B1 = R3/(R1+R2+R3)

V_B2 = (R2+R3)/(R1+R2+R3)

V_E1 = V_B1 - V_BE

V_E2 = V_B2 - V_BE

V_C1 = V_E2

V_C2 = VP - I_C*R_C

R_B1 = R3*(R1+R2)/(R1+R2+R3)

I_B*R_B1 + I_B*Beta*R_E + V_BE = V_B1

I_B = (V_B1 - V_BE)/(R_B1 + Beta*R_E)

I_C = Beta*I_B

g_m = Ic/25mA

r_π = Beta/g_m

If RE2 is zero ohms:

A = -g_m*((RL||RC)*(R2||R3))/(R23+RS)*(r_π/(r_π+Rx+(R2||R3||RS))

else

A = -(RL||RC)/RE2

Rx is typically 10-30 ohms, we use 20 in the calculator.

f_T = g_m/(2π*(C_BE+C_BC))

f₁ = 1/(Rin*(Cbe+2*Ccb))/(2*π)

f₂ = 1/(R_L*Ccb)/(2*π)

The lower pole is dominate:

BW = f₁