After a brief history of electronics starting with valves and vacuum tubes, this program explains the operation of semiconductors, diodes, and transistors. It covers the electronic band structure of conductors, insulators, and semiconductors; doping to boost the conductivity of n- and p-type semiconductors; the functioning of LEDs and photodiodes used in remote-control devices and DVD readers; how NPN transistors work; and the action of MOSFETs, core components in the integrated circuits that control computers, phones, and all other electronic devices. A viewable/printable worksheet is available online. (22 minutes)