control loop

Hello, I am working on PSFB DC-DC converter and I prefer analog control so I need to pick a op-amp for type 2 compansation . I also add buffer op-amps in current or voltage feedback paths for stability. Which specifications should I concern for fast response ? and Can you give an example...

Specifically, I am curious why the control loop must be broken such that one side of the break is high impedance while the other side is low impedance and if this applies to more than just power electronics. I've read several app notes including TIs AN-1889 (Step 1: Setting up the Circuit...