The transistor officially was invented in 1948 at Bell Laboratories, the brainchild of a team of researchers including William Shockley and Gerald Pearsons. Unofficially, both men relied heavily on concepts drawn from the work of Canadian inventor Julius Lillienfield, who patented a similar idea in 1925.
Prior to the availability of semiconductor devices, electronics systems depended completely upon vacuum tubes as active components. Running on large amounts of electrical energy, tube systems required large power supplies and a way to vent waste heat, limiting the complexity of electronic designs.
With significantly lower levels of power consumption, transistors revolutionized the electronics industry. Computing devices that once occupied entire buildings were quickly reduced to briefcase size by replacing vacuum tube systems with transistorized engineering.
Bipolar transistors are sandwiches of crystalline material, "doped" with specific elements to enhance conductivity. NPN transistors contain a negatively polarized layer between two positively polarized layers; PNP transistors have the opposite polarity of construction.
The three layers of bipolar transistors are the collector, base and emitter. With other components to limit electrical flow through the device, a small controlling voltage applied to the base or center layer has an amplified effect on the current flowing through collector and emitter.
Although the first transistors were created from layers of germanium, most in industrial use today are silicon based, with some high frequency devices manufactured from gallium arsenide. As the technology has improved, transistors of advanced design have replaced or augmented the original bipolar transistor models.