why is it an in-phase zero?

[coolsummer]

The book says: "CFF is to feed forward small signals from Vo to feedback node VFS. This introduces an in-phase zero ZFF that helps save phase near the unitygain frequency of the system. "
But the base of Q1(VA) is inverting input, VA and Vo are out of phase, so CFF should introduce a right-half plane zero, which degenerates the frequency response. Where am I wrong?

 

[FvM]

CFF is part of the feedback network. I'd call it a lead or lead-lag circuit. It raises the loop phase in a limited frequency interval to increase the phase margin. I think that the term feedforward is misleading in this context. But beyond terms, the circuit surely involves no right half-plane zero.

--- Updated Apr 10, 2022 ---

The TI application is discussing a similar setup https://www.ti.com/lit/pdf/sbva042