##### From Intuitive Analog Circuit Design

## In This Chapter

The basics of bipolar devices are covered, including basic semiconductor physics, ^{[1]} the concepts of electron and hole flow in semiconductors, the differences between drift and diffusion flow, generation and recombination, and the effects of semiconductor doping on carrier concentrations. We finish with a discussion of the ideal diode, and illustrate how a diode can conduct forward current, but can also block reverse voltage. Detailed mathematical derivations are avoided wherever possible. However, enough mathematical detail is given so that the reader can discern the important scaling laws and functional dependencies of the ideal diode. At the end of the chapter we ll discuss some of the factors that result in nonideal behavior in diodes. We ll conclude with a discussion of load lines, a useful method for solving for the operating point of circuits with nonlinear devices. The load-line technique will be useful in later chapters in analyzing transistors.

^{[1]} We will not go into the quantum mechanics of semiconductors, which provides the rigorous analyses. The simpler models developed in this chapter hopefully will give insight into the basics of semiconductor operation. Excellent reviews of semiconductor physics are given in Shockley s and Bardeen s 1956 Nobel prize lectures, with reference given at the end of this chapter.

## Current Flow in Insulators, Good Conductors and Semiconductors

In nature, from the point of view of the ease of producing current flow in a material, there are three broad classes of materials: insulators, conductors and semiconductors. Semiconductors and metals can support...

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