The transistor replaced vacuum tubes, allowing the size of computers to decrease dramatically while their power increased. Despite this triumph, Bardeen was unhappy with Shockley, whom he felt was limiting his and Brattain's involvement with further refinements to the transistor. Bardeen took a position at the University of Illinois at Urbana-Champaign.
What Happened on July 24th
july 24, 1951 Transistor Inventor Leaves Bell Labs
John Bardeen notified AT&T Bell Laboratories that he would be leaving the company where, along with Walter Brattain and William Shockley, he had developed one of the most essential components of modern computing: the point-contact transistor.