申論題

2.(25%) Consider the voltage amplifier of Figure 2 with a BJT device having β =100 when it is biased in the active region, the AC signal voltage Vsig, signal resistance = 10kΩ and coupling capacitors and which can block DC component and pass AC component. The voltage supplies = 10V and the thermal voltage V_T= 25mV. The constant voltage drop 0.7V approximation can be used for the turn- on of a p-n junction, and the constant voltage drop ~ 0.2V approximation can be used when the BJT is biased in the saturation region. In addition, other resistances are also included, such like R₁ = 2MΩ, R₂ = 2MΩ, R_E = 5kΩ, R_c = 5kΩ, R_L= 5kΩ. Please come out following parameters: (a) transconductance gm, (b) input resistance, (c) overall AC voltage gain (d) Please describe the advantages of the existing of emitter resistance Re compared with no R_E. (5%, 5%, 5%, 10%)