6. (25%) Consider the voltage amplifier of Fig. 6 with a BJT device having β = 100 when it is biased in the active region. The coupling capacitors C₁ = C₂ = C₃ = 1 μF. The voltage supplies are 5 V and the thermal voltage VT= 25.9 mV. If the transistor is specified to have f_T = 700 MHz and C_μ = 1 pi. The constant voltage drop 0.7 V approximation can be used for the turn-on of a p-n junction. In addition. other resistances are also included in the Fig. 6. Please calculate (a)f₁，f₂，f₃ (let f₁ ＜f₂＜f₃) values of the low-frequcncy transfer function (b) the upper 3-dB frequcncy f_Hby using open-circuit time constants method if the ro and rx effect are neglected. (5%*3, 10%)

5. (25%) Consider the voltage amplifier of Fig. 5 with two BJT devices: Q1 and Q2, having β= 100 when they are biased in the active region. The coupling capacitors C can block DC component and pass AC component. The voltage supplies are 10 V and the thermal voltage V_T = 25.9 mV. The constant voltage drop 0.7 V approximation can be used for the turn-on of a p-n junction. In addition, other resistances are also included in the Fig. 5. Please come out the following parameters: (a) DC base voltage of Q1:, (b) DC base voltage of Q2: , (c) DC collector voltage of Q2: . (d) overall AC voltage gain. (5%, 5%, 5%, 10%) 

4. (15%) Consider the yoltage amplifier of Fig. 4 with a MOSFET specified to have Vt=  1.5 V, (WIL) = 0.5 mArV², andλ = 0.02. The coupling capacitors C can block DC component and pass AC component. Calculate (a) the small-signal voltage gain (b) its input resistance , and (O) the largest allowable input signal. (5%*3)