OVERVIEW

In 1947, a research team at Bell Laboratories invented a solid-state device whose resistance between two output terminals could be controlled by a third input terminal. This three-terminal device was named transistor, shortened from the words transfer res istor. Today, this device is known as a bipolar junction transistor (BJT). The BJT was the first minute solid-state device to provide implementations of electrically controlled switch and amplifier of electrical signals. The fact that these two important functions could be performed by a minute device triggered the development of microelectronics.

Many more different types of solid-state transistors appeared after the BJT. A metal-oxide-semiconductor field-effect transistor (MOSFET), developed in 1960, would become the most used electronic device ever. It enabled development of digital circuits of very large-scale integration (VLSI), the building blocks of computers. Other types of field-effect transistors (FETs), like metal-semiconductor FETs (MESFETs) and high-electron mobility transistors (HEMTs) were subsequently developed for some specific applications, especially high-frequency digital and microwave analog applications.

As a common feature, all types of transistors can perform the following two functions: (1) voltage-controlled switch and (2) voltage-controlled current source. The first function represents the building block of digital circuits and the second function enables construction of different types of linear amplifiers.

Using the concepts of voltage-controlled current source and voltage-controlled switch, this chapter introduces the basic applications of transistors in a generic way. This approach, where the applications are described before the particular devices, clearly defines...