It is an hour phone interview. It started with the interviewer describing about his group and a few behavioral questions. Then, it followed with about twenty technical questions that were mostly about circuit analysis and device physics. To do well, you will have to be very familiar with most of the basic circuit courses you have taken before. I did not perform well, and I even realized most of the answers I gave were wrong immediately after the phone interview (mainly due to nervousness and lack of confidence). Overall, the interview was fair.