申論題

4. (30%) Figure 4 shows a CC-CE amplifier with = R_L = 5 kΩ, I₁ = I₂ = 1mA, and identical transistors with β = 100, f_T = 500 MHz, Cμ = 5pF, and Cc = 2uF. The thermal voltage V_T= 25mV. For simplicity, neglect r_o and r_x effect. Please find (a) the input resistance(b) the midband gain A_M, (c) the C_πof the BJTs, and (d) 3-dB frequency of the upper end of the midband, f_H (using open-circuit time- constants method). (5%, 5%, 5%, 15%)