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翻开有关三点式振荡器的书籍,可以清楚地查到三点式振荡器的起振条件: 式中h_(fe)为晶体管的电流放大系数。现在所谈的振荡器,其发射极串有电流负反馈电阻R_e(见图)。此振荡器的起振条件,是h_(FE)≥2X_1/X_2,正巧为原来无R_e时的二倍。根据振荡器振荡条件:Kβ=1,对于该振荡器,我们将e、c端视作输出端,b、e端视作输入端,则输入阻抗 (1)等效信号源内阻Z_3可以视为Z′_1与(Z_2+Z_3)的并联值:
Open the book on the three-point oscillator, you can clearly find the three-point oscillator start-up conditions: Where h_ (fe) for the transistor current amplification factor. Now talking about the oscillator, the emitter string current negative feedback resistor R_e (see Figure). The oscillator start-up conditions, h_ (FE) ≥ 2X_1 / X_2, happened to be doubled when no original R_e. According to the oscillation condition of the oscillator: Kβ = 1, for the oscillator, we regard e and c terminals as output terminals and b and e terminals as input terminals. The input impedance (1) equivalent signal source internal resistance Z_3 can be regarded as Parallel values of Z'_1 and (Z_2 + Z_3):