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一、两级负反馈 (一)串联反馈图1示单级串联负反馈放大器,反馈电阻R_E既串联于输出回路,又串联于输入回路.反馈是由输出电流流经R_E产生的,如无输出电流,就没有反馈;同时,R_E上产生的电压降与输入信号电压极性相反,有抵消作用,故这种反馈是负反馈,它是电流输出一电压输入的反馈.电阻R_E大,表示反馈强;为了获得较强的反馈,负载电阻R_L宜小,使输出电流大,R_E上电压降大;而信号源内阻R_S宜小,信号源近于电压
1, two negative feedback (A) series feedback Figure 1 shows a single-stage series negative feedback amplifier, the feedback resistor R_E is connected in series with the output loop, but also in series with the input loop feedback generated by the output current R_E, if no output Current, there is no feedback; the same time, R_E voltage drop generated by the opposite polarity of the input signal voltage, there is offset, so this feedback is negative feedback, it is the current output of a voltage input feedback .R_E large resistance In order to obtain strong feedback, the load resistor R_L should be small, so that the output current, R_E on the voltage drop; and signal source resistance R_S should be small, the signal source close to the voltage