I got this interview through a job posting on my college's career website. The first interview was on-campus and the interviewer asked me questions about my resume and a simple digital circuit question. It was really relaxing. I received my second interview about a month later and it was on phone. It was with my supervisor and we talked about the projects that I have worked on in my classes. It was only 20 minutes long, more like a screening process. My last interview was two weeks later, which was on phone again. It was 40 minutes of technical questions. Questions ranged from MOSFETS to inverters to linear algebra, but they were all really simple. For instance, I was asked to describe an NMOS and a PMOS, to describe the function of a circuit with either odd or even number of inverters, etc. I didn't know how to answer every question, for instance the linear algebra ones, but it didn't hurt my performance. As long as you can answer as many possible then you should be fine. Didn't receive my offer until a month later though, so don't panic if you didn't hear back. Just follow up with them!