Overview

The theme of this chapter is to provide the reader with a more comprehensive historical background of the operational amplifier (op amp for short see below). This story begins back in the vacuum tube era and continues until today (2004). While most of today's op amp users are probably somewhat familiar with integrated circuit (IC) op amp history, considerably fewer are familiar with the non-IC solid-state op amp. Even more likely, very few are familiar with the origins of the op amp in vacuum tube form, even if they are old enough to have used some of those devices in the '50s or '60s. This introduction addresses these issues with a narrative of not only how op amps originated and evolved, but also what key factors gave rise to the op amp's origin in the first place. ^[1]

A developmental background of the op amp begins early in the twentieth century, starting with certain fundamental beginnings. Of these, there were two key inventions very early in the century. The first was not an amplifier, but a two-element vacuum-tube-based rectifier, the "Fleming diode," by J. A. Fleming, patented in 1904 (see Reference ^[1]). This was an evolutionary step beyond Edison's filament-based lamp, by virtue of the addition of a plate electrode, which (when positively biased) captured electrons emitted from the filament ( cathode). Since this device passed current in one direction only, it performed a rectification function. This patent was the culmination of Fleming's earlier...