Floating-Gate Circuits and Systems

Abstract

In this chapter, we will look into the whereabouts of floating-gate circuits and systems. Our goal is to present how floating-gate circuits may be used in a constructive way without any technological “special effects”. We will only briefly touch digital circuits and focus primarily on analog properties. The floating-gate MOS device is not new. Experiments on floating-gate devices from Fairchild Research Laboratories are reported as early as the mid1960s [1,27]. Some of the first published scientific reports dates back to 1967 [2]. In 1971, the first commercial product was announced and became known as EPROM [3] using a floating-gate avalanche-injection MOS (FAMOS) transistor. Since then floating-gate devices have been utilized in many digital systems. The Flash-EPROM of present computers is storing vital programs (BIOS) and parameters in a non-volatile way using floating-gate structures. With research in neural networks picking up in the 1980s, demand for analog non-volatile storage arise and floating-gate structures were obvious candidates [4,5]. Fundamentally the stored charge on a floating gate is an analog quantity, but finding ways to control this storage with sufficient precision has turned out to be difficult. In the following, we will briefly go through the fundamentals of floatinggate physics. Then, we will proceed with simple circuit elements. Finally, we will present some real working circuits and systems.