AI-5
MOSFET—A semiconductor device that contains diffused source and drain regions on either side of a P-
or N-channel area. Also contains a gate insulated from the channel area by silicon-oxide. Operates in
either the depletion or the enhancement mode.
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NEGATIVE TEMPERATURE COEFFICIENT—A characteristic of a semiconductor material, such
as silver sulfide, in which resistance to electrical current flow decreases as temperature increases.
NONLINEAR—Having an output that does not rise or fall directly with the input.
NPN—An NPN transistor is formed by introducing a thin region of P-type material between two regions
of N-type material.
OPTICAL COUPLER—A coupler composed of an LED and a photodiode and contained in a
light-conducting medium. Suitable for frequencies in the low-megahertz range.
OPTOELECTRONIC DEVICES—Devices that either produce or use light in their operation.
OVERDRIVEN—When the input signal amplitude is increased to the point that the transistor goes into
saturation and cutoff.
PENTAVALENT IMPURITY—A type of impurity which contains five valence electrons and donates
one electron to the doped material. Also called DONOR IMPURITY.
PHOTOCELL—A light-controlled variable resistor that has a light-to-dark resistance ratio of 1:1000.
Used in various types of control and timing circuits.
PHOTODIODE—A light-controlled variable resistor. Current flow increases when the PN junction is
exposed to an external light source
PHOTOTRANSISTOR—An optoelectronic device that conducts current when exposed to light.
Produces more current and is much more sensitive to light than the photodiode.
PHOTOVOLTAIC CELL (SOLAR CELL)—A device that acts much like a battery when exposed to
light and converts light energy into electrical energy.
POINT-CONTACT TRANSISTOR—A semiconductor diode that can work with and amplify the
ultrahigh frequencies used in radar.
POSITIVE TEMPERATURE COEFFICIENT—The characteristic of a conductor in which the
resistance increases as temperature increases.
POWER SUPPLY—A unit that supplies electrical power to another unit. It changes ac to dc and
maintains a constant voltage output within limits.
PRINTED CIRCUIT BOARD—A flat insulating surface upon which printed wiring and miniaturized
components are connected in a predetermined design and attached to a common base.
QUANTUM-MECHANICAL TUNNELING—When an electron is able to cross a PN junction because
of tunnel effect.
QUIESCENCE—The operating condition of a circuit when no input signal is being applied to the
circuit.
