Hi Pancho
Quote:Contribution of fricker noise to sideband noise could be larger for sharp transition since conversion gain is larger.
After thinking about this a little bit, I completely agree with you - this could be the reason. Basically stationary noise sources get convolved with response of the circuit to give your usb noise behaviour.
If flicker noise comes down with with increasing W, and USB noise increases with W, then the spectral components (fourier components, not PSD) at the output of your hysteretic invertor must increase by factor between varying between W^1/2 and W (a first order calculation). Is this the case for your circuit?