此处电容是否可以省掉

zhengjq01

bandgap

请教高手，从理论上看这个电容可以去掉,为啥要加上这个电容,从上电环路上分析分析零极点没有意思，因为开环增益<1.望高手解答疑惑！

billlin

1.>This is Decoupling Capacitor, the Purpose is to make OP of the PSRR Better.
2.> you can simulate the OP PSRR, with this Decoupling Capacitor , the PSRR better.
3.> Generally, Always at Decoupling Capacitor at "BIAS node"

zhengjq01

回复 2# billlin

您好，我刚刚做了一个仿真，条件为是否加上上图中的电容，发现没有这个电容PSRR和加上电容PSRR 结果一样，请看下面仿真结果图

PSRR 仿真结果图

billlin

You can try Power(AVDD) has a Step Response
AVDD+200mV --> AVDD-200mV --> AVDD+200mV to see if has different ?

zhengjq01

回复 4# billlin

仿真的时候对VDD加的是1V step response，加200mV step Response ，PSRR在是否有电容的情况下还是一样。

billlin

the AVDD decoupling Capacitor should be workable if the AVDD has a step response Noise.
If the capacitor value too small ?
generally,
the capacitor value need greater than 1pF .