晶体管载波没备中的自动电平调节装置基本上都使用热电式的,即调节放大器中采用热敏电阻作为增益(或增益频率特性)的可调元件。自动调节时,将收到的导频与参考电平比较,并将其误差予以放大之后作为热敏电阻的加热电流,使其阻值变化而改变放大器的增益,达到调节的目的。这个闭环回路通常如图1所示。 Transistor carrier wave devices are basically automatic level adjustment device using the thermoelectric type, that is, the use of regulated amplifier thermistor as gain (or gain frequency characteristics) of the adjustable components. Automatic adjustment, the pilot will be received compared to the reference level, and its error is amplified as the thermistor heating current, so that the resistance changes to change the amplifier gain, to achieve the purpose of regulation. This closed-loop circuit is usually shown in Figure 1.