bias上的电容作用

何难

求帮忙看看这个bias中的电容C0什么作用呀，大小为100fF，是启动电路的作用吗？工作原理是怎样的呢？
谢谢大家帮忙解答或者提供给思路～～！！

tStone

去掉这个电容，跑一下各种coner下的上电过程，看一下会不会在某些情况下振荡。将这个电容加回去，再看下是不是振荡会消失。

camelotking

Thank you for sharing. This is a smart compensation.
Co provide both "startup" and "stability compensation" function.
(1) M1, M2, M3 form a positive feedback loop
(2) M3, M4, R are negative feedback loop
If VDD rise, gate of M1/M2 follow VDD but gate of M3 may stay at ground. the circuit won't start up. C0 can pull up the gate of M3, then the voltage of gate of M4 will be built
On the other side, C0 will also reduce the positive loop gain of (1).
This is my comment. Discussion is welcomed.
Add "iprobe" in the path of "gate of M3" to "M1/M4 drain" run "stb" to check phase margin with and without C0. You should be able to see the difference.

何难

tStone 发表于 2023-12-21 19:05
去掉这个电容，跑一下各种coner下的上电过程，看一下会不会在某些情况下振荡。将这个电容加回去，再看下是 ...

好的，我去仿真看看，谢谢！

何难

camelotking 发表于 2023-12-22 01:36
Thank you for sharing. This is a smart compensation.
Co provide both "startup" and "stability compe ...

Thank you very much for your answer. I have learned a lot！
I will conduct simulations to verify it~