Notes

Outline

Introduction to Electronics Active Devices

Diodes Silicon Diode A “one-way” valve Zener diode These are specially made with low (accurate) peak inverse voltages. They are used to give a reference voltage

Doping Semiconductors The addition of a small percentage of foreign atoms in the regular crystal lattice of silicon or germanium produces dramatic changes in their electrical properties, producing n-type and p-type semiconductors. Pentavalent impurities (5 valence electrons) produce n-type semi-conductors by contributing extra electrons. Trivalent impurities  (3 valence electrons) produce p-type semiconductors by producing a "hole" or electron deficiency.

Depletion Region When a p-n junction is formed, some of the free electrons in the n-region diffuse across the junction and combine with holes to form negative ions. In so doing they leave behind positive ions at the donor impurity sites.

Bipolar Transistor A current-controlled valve The current flow from collector to emitter is b (a high number) times the base current The base to emitter voltage is 0.7 V when the transistor is on.

Field Effect Transistors A voltage-controlled valve