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发表于 2008-4-29 23:43:30
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原帖由 guonanxiang 于 2008-3-26 15:31 发表
根据gray的说法,对于P输入,第一级与第二级电源对输出的影响相互抵消,因此PSRR+很好!
仔细研究page434~435,发现gray的推导有问题,对于pmos输入的二级标准运放,vdd的变化直接通过Rtail(电流源等效电阻)作用到 ...
Rtail is large enough, like source degeneration situation, just assume input small signal is equvient as a minus one on gate of differential pair, so after first stage, increase vgs of second stage, compensation the voltage result from vdd divide by second stage ro directly. |
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