申論題

4.(30%) Consider the BiCMOS amplifier shown in Fig. 4 has= 100 kΩ, R_G = 10 MΩ, Rs = 6.8 kΩ, R_c = 3kΩ, R_L= 1 kΩ, C_I= 0.1 μF, C₂ = 1 μF. The BJT has 0.7 V, β = 200, Cμ = 0.8 pF, f_T = 600 MHz, and thermal voltage V_T= 25 mV. The MOSFET has = 1 V, = 2 mA/V², and= 1 pF. Neglect the Early effect and channel length modulation effect. (a) Consider the DC bias circuit. Neglect the base current of Q2 in determining the current in Q1. Find the DC drain current in Q1 and collector current in Q2. (b) Consider the circuit at low frequencies. Deternine the frequency of the poles due to C1 and C2. (c) Consider the circuit at higher frequencies. Use open-circuit time constants to estimate f_H. (5%,5%,5%,5%,10%)