Can you mirror Ibias from node VBN where NMOS transistors are in weak inversion?

[tyanata]

I have designed the bias circuit shown in the picture. M1 and M2 are deeply in saturation, M3 and M4 are in weak inversion.

I know that, I can mirror Ibias from node VBP where PMOS tranzistors are in saturation.
My question is following: Is it possible to mirror Ibias from node VBN where NMOS tranzistors are in weak inversion.

 

[Btrend]

Re: bias question

weak inversion means that u have a small gm, also means ur ro is not large,
so ur PSRR_ will not be as good as in the strong inversion case.

 

[sunking]

bias question

Make Rbias big and try.

 

[gajen]

Re: bias question

Vnb will be very sensitive to voltage variation on the source side of current mirror. Any difference in the source of current mirror between the 2 will give high mismatch for the current due to devices being in sub-threshold.