Here's why it worked Germanium is a semiconductor and, if properly treated, can either let lots of current through or let none through. This germanium had an excess of electrons, but when an electric signal traveled in through the gold foil, it injected holes(the opposite of electrons) into the surface. This created a thin layer along the top of the germanium with too few electrons Semiconductors with too many electrons are known as N-type and semiconductors with too few electrons are known as p-type. The boundary between these two kinds of semiconductors is known as a P-N junction, and it's a crucial part of a transistor. In the presence of this unction current can start to flow from one side to the other In the case of Brattain s transistor, current flowed towards the second gold contact Think about what that means. A small current in through one contact changes the nature of the semiconductor so that a larger, separate current starts flowing across the germanium and out the second contact A little current can alter the flow of a much bigger one, effectively amplifying it. Of course, a transistor in a telephone or in a radio has to handle complex signals. The output contact cant just amplify a steady OE F Schubert, Rensselaer Polytechnic Institute, 2003© E. F. Schubert, Rensselaer Polytechnic Institute, 2003 6 Here’s why it worked: Germanium is a semiconductor and, if properly treated, can either let lots of current through or let none through. This germanium had an excess of electrons, but when an electric signal traveled in through the gold foil, it injected holes (the opposite of electrons) into the surface. This created a thin layer along the top of the germanium with too few electrons. Semiconductors with too many electrons are known as N-type and semiconductors with too few electrons are known as P-type. The boundary between these two kinds of semiconductors is known as a P-N junction, and it’s a crucial part of a transistor. In the presence of this junction, current can start to flow from one side to the other. In the case of Brattain’s transistor, current flowed towards the second gold contact. Think about what that means. A small current in through one contact changes the nature of the semiconductor so that a larger, separate current starts flowing across the germanium and out the second contact. A little current can alter the flow of a much bigger one, effectively amplifying it. Of course, a transistor in a telephone or in a radio has to handle complex signals. The output contact can’t just amplify a steady