How Transistors Work

The transistor is arguably the greatest invention of the last century, or perhaps, one of the greatest of all time. If it wasn't for transistors, we couldn't have developed smaller, faster and cheaper computers, telephones, GPS devices, radios, gaming consoles, smart televisions, routers and a device -- no larger than a human hand -- that integrates all these marvels under the same screen. Here's how they work.

References:
Book: The Quantum Universe: Everything that can happen does happen
http://www.pitt.edu/~qiw4/Academic/ME2082/Transistor%20Basics.pdf
http://hyperphysics.phy-astr.gsu.edu/hbase/Solids/trans.html