CHAPTER 3 Active Components and Integrated Circuits Transistors Modern active components are all based on transistors, which were invented in 1948 by Brittain, Bardeen, and Shockley. Before transistors came into extensive use, the main active components for electronic circuits were vacuum tubes (called valves in the UK), and these are still used for high-power transmitters. There are two main types of transistors, called bipolar transistors and field-effect transistors (FETs), and since the bipolar type came first into use, we will start with that. Most modern electronics systems now, however, are based on the FET, usually in integrated circuit (IC) form. The transistor is a component that is created using a semiconductor crystal, and in a sense it is the inevitable result of the use of crystals in radio reception in the 1920s, because this started a line of research into crystal behavior which led to the transistor, even though the materials are quite different.