109年 - 108 國立中山大學_碩士班招生考試_電機系(甲組)：電子學#124112

1. (15%) We want to analyze the circuit of Fig. 1 to determine the collector voltage V_c, collector current I_c, and emitter voltage V_E. The minimum value of β is specified to be 30. (5%*3)

2. (25%) As shown in Fig. 2, a bipolar differential amplifier utilizes a current source (i.e., a single CE transistor Q₅) to supply a bias current 240 µA, and current-source loads formed by pnp transistors (Q₃and Q₄). For all transistors, β = 100 and early voltage |V_A| = 10 V. Find (a) gm of Q₁, (b) differential gain A_d, (c) input resistance of differential mode R_id and common mode R_icm, (d) CMRR(dB) if the two load transistors exhibit a 1% mismatch in their ro. Thermal voltage is 25 mV. (5%*5)

(a) Find the overdrive voltage Vov and gm of Q₁.

(b) Find the differential gain A_d and common mode gain A_icm if the drain resistors have 1% mismatch.

(c) If the input signal source has a small resistance R_sig and thus the frequency response is determined primarily by the output pole, estimate the 3-dB frequency f_H.

(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)

4. (30%) Consider a bipolar active-loaded CE amplifier having the load current source implemented with a pnp transistor, Let the circuit be operating at a 1-mA bias current. The transistors are specified as follows: β(npn) = 200, early voltage V_An = 150 V, |V_Apl = 100 V, C_π = 15 pF, C_µ = 0.4 pF, C_L = 5pF, and base resistance r_x = 200 Ω. The amplifier is fed with a signal source having a resistance of 30 kΩ. Determine (a) midband gain A_M, (b) input capacitor Cin and high-frequency response fH using the Miller effect, (c) f_H using open-circuit time constants, (d) the frequency of the transmission zero f_z,and (e) the gain-bandwidth product. Thermal voltage is 25 mV. (5%*6)