In this Control Loop Cookbook from TI, in the red box the author said that the crossover frequency (indicated in figure 2) of the open-loop is same as 3dB down frequency or corner frequency of the closed loop.
However, I don't think this statement is correct with the specific case in figure 2. The statement is only correct if feedback factor Kfb is unity. But from the closed-loop gain, we can infer that Kfb is not 1 (Kfb = 0.5).
What do you think about this? Is the article wrong? In general case, the crossover frequency of open-loop fc(actually I think call it "loop gain" is more accurate) makes the closed loop corner frequency at Kfb*fc.