ABSTRACT
Before the invention of the transistor in 1947 at Bell Laboratories by John Bardeen, Walter H. Brattain, and William B. Shockley, vacuum tubes were the workhorse of electronics. Vacuum tubes were bulky and fragile, required high voltage (>45 V) and a heater current to operate, and had lifetimes comparable to electric light bulbs. It is certainly no exaggeration to say that the transistor made possible modern solid-state electronics. Transistors serve much the same function as the old vacuum tubes but are much smaller, rugged, operate on low voltages, and have virtually infinite lifetimes. Once the purification and processing technology required to make transistors was
developed, a virtual explosion of new concepts became possible resulting in a vast array of new electronic and photonic devices, a few of which will be described in this chapter.
22.1.1 Bipolar Junction Transistor (BJT)
