Analysis

1. 单管共射放大电路

$V_{cc} = I_B R_b + U_{BE}$

$V_{cc} = I_C R_c + U_{CE}$

$I_E \approx I_C = \beta I_B$

2. 微变等效电路

$r_{be} \approx 300 + \beta \frac{26 mv}{I_C}$

3. 动态指标

$A_u = \frac{U_o}{U_i} = \frac{- \beta i_b \cdot (R_C // R_L)}{i_b \cdot r_{be}} = \frac{- \beta \cdot (R_C // R_L)}{r_{be}}$

$A_u$ 是放大倍数，对应的还有 $A_i$