Semiconductor Fundamentals Unit 1 – Introduction to Semiconductors
The SEMICONDUCTOR DEVICES circuit board has eight circuit blocks. Each circuit block
consists of an arrangement of diodes and/or transistors that gives you an understanding of how a
semiconductor functions in a practical application. This unit introduces you to semiconductors
and the functional circuit blocks on the SEMICONDUCTOR DEVICES circuit board.
Subsequent units are dedicated to each of the eight circuit blocks and to troubleshooting
semiconductor circuits.
NEW TERMS AND WORDS
diodes - semiconductor devices consisting of P type material and N type material.
transistors - devices consisting of NPN or PNP semiconductor layers. Transistors allow a small
current to control the flow of a larger current.
semiconductor - a material, usually silicon or germanium, doped with impurities to create a
compound whose electrical resistance is greater than that of conductors but less than that offered
by insulators.
doping - the deliberate introduction of a specific type of impurity into very pure base material.
Doping is accomplished by many different processes, but it is always carefully controlled to
produce semiconductors with specific properties.
N type material - pure semiconductor material which has been doped with an impurity that
introduces free electrons into the semiconductor. The atoms of the doping material, sometimes
referred to as donor material, usually have a valence ring that contains one electron more than
those required to complete covalent bonds with base material atoms.
valence ring - the outermost electrons surrounding the nucleus of any atom. These electrons
interact with the valence electrons of neighboring electrons and are the main influences on the
electrical characteristics of the element.
P type material - pure semiconductor material which has been doped with an impurity that
introduces apparent positive charges (holes) into the semiconductor. The atoms of the doping
material, sometimes called acceptor material, usually have a valence ring that lacks one electron
from those necessary to complete covalent bonds with base material atoms.
free electrons - "extra" valence ring electrons that are not incorporated into covalent bonds.
These electrons result from doping pure base material with an N type impurity. They act as
current carriers in N type semiconductor material.
majority carriers - charges deliberately introduced into semiconductors to act as current carriers.
Electrons are the majority carriers in N type material; holes are considered to be the majority
carriers in P type material.
holes - positive charges in semiconductors resulting from incomplete covalent bonds. Holes
occur when pure base material is doped with a P type impurity.
anode - the diode region doped with P (positive) type material.
cathode - the diode region doped with N (negative) material.
zener - a diode designed to maintain a relatively constant voltage drop over a range of current
flows. Zeners are supplied in the same packages as "ordinary" diodes, but they operate in a
different way.
light-emitting diodes - (LED) a diode constructed to release energy in the form of light when
supplied with an electric current. The materials used in the construction of an LED determine the
color and brightness of the light.