By January 1948, he’d conceptualized a new type of transistor, made up of three chunks of semiconductor material. The outer two chunks would have a surplus of electrons; the piece sandwiched between them would have a deficit. If a tiny current was applied to the middle layer in the sandwich, it set a much larger current flowing across the entire device. This conversion of a small current into a large one was the same amplification process that Brattain and Bardeen’s transistor had demonstrated.
