Introduction to the BJT

Abstract

The ability to amplify electrical signals is a relatively recent discovery, starting with the invention of the vacuum tube in the early twentieth century. The vacuum tube, however, is both large and power hungry; it works by heating a filament to high temperatures, akin to incandescent light bulbs. The search was on for a device that can perform electronic amplification more efficiently, and this culminated with the successful demonstration of the first transistor at Bell Labs in New Jersey, USA, in 1947. The bipolar junction transistor (BJT) was the workhorse of the electronics industry until the 1990s, and even today, this transistor is used due to engineers’ familiarity with it. The body of work associated with the BJT is so large that it warrants study by all circuit designers.