Diode Characteristics

Chapter 9.12 Diode Characteristics

Fundamental Electrical and Electronic Principles Third Edition Book
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Fundamental Electrical and Electronic Principles Third Edition Book

  • 274Fundamental Electrical and Electronic Principlesas an insulator, and is called the depletion layer. There has been a redistribution of charge within the semiconductor, but since the circuit has an insulating layer in it, current cannot fl ow. The diode is said to be in its blocking mode. However, there is no such thing as a perfect insulator, and the depletion layer is no exception. Although all the mobile charge carriers provided by the doping process have been swept to opposite ends of the semiconductor, there will still be some thermally generated electron-hole pairs. If such a pair is generated in the p-type region, the electron will be swept across the junction by the electric fi eld of the battery. Similarly, if the pair is generated in the n-type, the hole will be swept across the junction. Thus a very small reverse current (in the order of microamps) will fl ow, and is known as the reverse leakage current. Since this leakge current is the result of thermally generated electron-hole pairs, then as the temperature is increased so too will the leakage current. 9.12 Diode Characteristics The characteristics of a device such as a diode can be best illustrated by means of a graph (or graphs) of the current fl ow through it versus applied voltage. Circuits for determining both the forward and reverse characteristics are shown in Fig. 9.14 . depletionlayerpn Fig. 9.13 ARRV1(a) Forward biasV Fig. 9.14 ARRV1(b) Reverse biasV