Does anyone who has ever used balun to simulate fully differential opamp with SC CMFB?

For DC Gain analysis, how to build up the test bench?
EE240 has one slide like that(DC_Gain_Bias, as in the attachment1).
The SC CMFB is introduced in Ken Martin's book(cmfb,as in the attachment2).

Here comes my questions:
1)How to deal with the SC CMFB during AC analysis? That is, how to connect non-overlapping clock(ph1,ph2)?
2)How to deal with the Vbias in the attachment2?

Thanks.

SpectreRF's PAC analysis.

I have write a verilogA module to replace the SC CMFB part and run the AC simulation, the results seems to be reasonable.

Whenever I want a simple AC, STB,  or XF with the SC CMFB, I break the feedback from the SC CMFB and replace it with a continuous time CMFB model.  This gives me a very fast way of verifying the differential signal path of the amp.  Since I am normally making switched cap circuits anyway, I can verify the operation of the SC CMFB at a higher level where the time penalty of running a PXF or PSTB is already going to be spent.