O'Brien also announced that John Butler, who was promoted to defensive coordinator last month after Ted Roof left Penn State, will continue to coach the cornerbacks.
"Anthony will be a great addition to our staff," O'Brien said in a statement. "He is an experienced and passionate defensive coach and recruiter. We welcome Anthony to our team and look forward to his contributions to the program."
Midget, a Florida native, was a three-year starter under Frank Beamer at Virginia Tech in the late 1990s. He has served as an assistant at Lake Worth (Fla.) High school, Virginia Tech and Georgia State. Midget was Georgia State's defensive coordinator in 2012.