In this chapter we introduce the fundamentals of the operational amplifier, or op amp, as it is commonly known. We will investigate the construction and usage of a typical general-purpose op amp. Specific along with generalized internal circuits and associated block diagrams are examined. An initial op amp data sheet interpretation is given as well. Toward the middle of the chapter, the first op amp circuit examples are presented. The chapter finishes with an explanation of semiconductor integration and construction techniques. After finishing this chapter, you should be familiar with the concepts of what an op amp is composed of, how it is manufactured, and a beginning idea of how it might be used in application circuit design.