I'm trying to follow the procedure in
AN-1889 for measuring the feedback loop gain in a power converter. A transformer is used to couple a function generator signal across a small resistor without passing DC, but I'm not sure what kind of transformer to use. The note says "There are special transformers for such measurements available, which offer a very flat voltage transmission over a wide frequency band." What kinds of commercially available transformers specifically fit this bill? I was browsing Digikey and thought maybe things under current-sense transformers or pulse transformers seem like they could work. Has anyone done this and have recommendations?