A problem about Class-AB output stage

[Ziqi]

Hi, friends

This Class-AB output stage circuit worked in open-loop condition to drive a 50ohm load. But the fn noise contributed by the MOS in red circle is too strong, nearly 50% contribution. The output integrated noise below 1MHz is about 0.17mV. the bias current in output branch is about 2.5mA.

I think the most noisy MOS is just for biasing, but I dont know how to reduce its noise.

Thanks

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This another type circuit is tried, the low-frequency noise performance is even worse. the MOSs in red circles are most noisy(fliker noise).
Could you help me how to deal with the LF noise?

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This output noise spectrum like this. my interested band is from 1MHz to 500MHz. but the fn noise dominant.

 

[FvM]

There are many ways to reduce the current mirror noise contribution, e.g. degeneration resistors or larger bypass capcitors.