A transistor works by changing its resistance between the amount of power going in and the power going out, depending on how much current flows through the base to the emitter. Transistors can amplify electronic signals and precisely control the amount of current going through the circuit.
All modern electronic devices use transistors to control the flow of electricity within different internal components. Prior to the invention of transistors, electronic devices relied on vacuum tubes, which were bulky and less efficient compared to transistors. In order to work correctly, transistors require pure semiconductor materials such as germanium. A process called doping is used to change germanium into a weak conductor, or semiconductor, which has properties of insulators and conductors. Semiconductors allow electrical conductivity in varying degrees and results in a germanium layer that is either a negative type (N-type), or positive type (P-type). N-type layers make it easier for electrons to surge out because the doping element adds electrons to the germanium. P-type layers cause the germanium to lose electrons, which causes adjacent materials to flow towards it. Placing an N-type layer next to a P-type layer forms a P-N diode. Ultimately, this diode allows an electrical current to flow in one direction.