Diodes and Transistors

silicon diode

used in rectification

zener diode

voltage regulator

light emitting diode

used in indicators

forward bias

small resistance to current flow in one direction

reverse bias

resistance extremely high if current goes backwards

transistor switch

a semi-conductor that amplifies a signal from a sensor

base

middle section of transistor, lightly doped to reduce

collector

positive lead of transistor, always reversed biased so that charge carriers move away from the base, moderately doped

emitter

main function is to supply majority of charge carriers to base

doping

process of introducing an atom of another element to the lattice of a pure material

p-doping

process in which the structure is doped with atoms that have 3 electrons in outer shell - creates holes so that current can be conducted as accept electrons from other atoms

n-doping

process in which the structure is doped with atoms that have 5 electrons in outer shell - extra electron allows for conduction as it is free to roam

semiconductor outer shell

4 electrons, performs perfect covalent bonds