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对于NRZ(不归零)信号,比起直流放大来,人们更偏爱用交流放大,因为交流放大一般更为经济一些,而且抗漂移能力也更强。但是交流处理过程也有其缺点,那就是交流耦合会消除数字数据流的直流参考电平。如图1所示,如果在放大器的输入端出现一长串1或0的信号流,在输入端经过由RC时间常数确定的一段时间后,输出就会下降。由于有这样的问题,就不得不在交流放大器后面加一个直流还原电路。图2所示电路将放大器消除的直流电平加以还原,并避
For NRZ (non-return to zero) signals, people prefer to use AC amplification over DC amplification because AC amplification is generally more economical and more immune to drift. However, there is also the disadvantage of the AC processing that AC coupling eliminates the DC reference level of the digital data stream. As shown in Figure 1, if a long signal stream of 1 or 0 appears at the amplifier’s input, the output goes down after the input has been subjected to a period of time determined by the RC time constant. Because of such problems, we have to add a DC reduction circuit behind the amplifier. The circuit shown in Figure 2 will restore the amplifier to eliminate the DC level and avoid