申論題

3. (30%) A MOSFET differential amplifier as shown in Fig. 3 is biased with a current I = 1 mA. The transistors Q₁ and Q₂ have W/L = 100, µ_nC_ox = 0.25 mA/V², V_A = 20 V, C_gs = 60 fF, C_gd = 15 fF, and C_db = 15 fF. The drain resistors R_D are 5 kΩ each. R_ss = 25 kΩ. Also, there is a 100-fF capacitive load between each drain and ground.

(d) If, in a different situation, the amplifier is fed symmetrically with a signal source of 20 kΩ resistance (i.e., 10 kΩ in series with each gate terminal), use the open-circuit time-constants method to estimate f_H. (5%*6)