Hello everyone,
I'm currently designing and simulating an Inverting Buck Boost (IBB) converter using a LT3845 controller. Right now I'm working on extracting the Bode plot to ensure the converter is stable and the RHPZ effect is kept at bay, but I'm facing some technical difficulties in using LTSpice's FRA component here. Following the tips in [AN-2579](https://www.analog.com/en/resources/app-notes/an-2579.html) I tried placing the .FRA component, where the signal is injected, in the lower leg of the feedback loop but got the following error (which, to be honest, I have no idea what is suggesting me to do):
FRA Instance @1 has a grounded terminal, with no refnode specified or an associated fraprobe device.
Do you have any tip to correctly perform this kind of measurement using LTSpice?
Thanks in advance.
