Introduction
The basic principle of the field-effect transistor (FET) has been known since J. E. Lilienfeld’s patent of 1925. The theoretical description of a FET made by Shockley in 1952 paved the way for development of a classic electronic device which provides the designer the means to accomplish nearly every circuit function. At one time, the field-effect transistor was known as a “unipolar” transistor. The term refers to the fact that current is transported by carriers of one polarity (majority), whereas in the conventional bipolar transistor carriers of both polarities (majority and minority) are involved.