申論題

4.(30%) Figure 3 shows the common-source amplifer with an ideal current source I = 0.4 mA, = 200 kΩ, R_G = 2 MΩ, R_D =R_L = 20 kΩ, C₁ = C₂ = C₃ = 1 HF. The MOSFET has the device parameters: I = 0.2 μm, W = 2 μm, = 10 fP/μm², μn = 450 cm²/V-s, r₀ = 100 kΩ, = 3.2 fF, can be neglected, and the source terminal of MOSFET is connected to its body terminal. Please calculate (1) the transconductance gm of the MOSFET, (2) the A_M，  f₁，f₂，f₃ (let f₁ ＜f₂＜f₃) values of the overall low- frequency transfer function , (3) the upper 3-dB frequency fr by using open-circuit time constants method. (5%, 5%*4, 5%)