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在需要高增益放大的场所,应用普通多级放大器往往对电源纹波要求很严。因为前级的集电极阻抗将电源纹波引导到后级的输入端,在后级的输出端以放大了的形式出现;而且级与级之间往往需要加强退耦,以免通过电源耦合引起自激;另外若要组成高开环增益的负反馈放大器的话,则由于多次级间耦合引起的相移的累积,往往使反馈环内对某一频率呈现360°相移而成为正反馈,造成不稳定。因此采用有一定抑制电源纹波影响和电源耦合能力的单级高增益放大器是比较合适的。电路介绍图1电路中,BG_1管作恒流源,基极由稳压管D_1再经R_2C_1滤波供电,以保证基极电流恒定不变。对于
In places where high gain amplification is required, applying common multistage amplifiers often places strict demands on the power supply ripple. Because the front-stage collector impedance leads the power supply ripple to the input of the rear stage, it appears in an enlarged form at the output of the rear stage, and the decoupling tends to be enhanced between stages to avoid self-coupling In addition, to form a negative feedback amplifier with a high open-loop gain, the accumulation of phase shifts caused by multiple interstage coupling often makes the feedback loop have a 360 ° phase shift to a certain frequency and becomes a positive feedback, resulting in instability . Therefore, it is more appropriate to adopt a single-stage high-gain amplifier that has a certain effect of suppressing power supply ripple and power coupling. Circuit description Figure 1 circuit, BG_1 tube as a constant current source, the base by the regulator D_1 and then R_2C_1 filter power supply to ensure that the base current is constant. for