An integrated-circuit npn transistor has the following measured characteristics: r b = 100, r c = 100,

An integrated-circuit npn transistor has the following measured characteristics: r_b = 100Ω, r_c = 100Ω, β₀ = 100, r_o = 50 kΩ at I_C =1 mA, f_T = 600 MHz with I_C = 1 mA and V_CB = 10 V, f_T = 1 GHz with I_C = 10 mA and V_CB = 10 V, C_μ = 0.15 pF with V_CB = 10 V, and C_cs = 1 pF with V_CS = 10 V. Assume ψ0 = 0.55 V for all junctions, and assume C_je is constant in the forward bias region. Use r_μ = 5β₀r_o.

(a) Form the complete small-signal equivalent circuit for this transistor at I_C = 0.1 mA, 1 mA, and 5 mA with V_CB = 2 V and V_CS = 15 V.

(b) Sketch the graph of f_T versus I_C for this transistor on log scales from 1 µA to 10 mA with V_CB = 2 V.