Technical
Glossary-A
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ABCD Parameters
The set of parameters for a two-port device that relates the input
voltage and current to the output voltage and current. The transfer function
of a cascaded circuit can be determined from the product of the ABCD parameters
for the individual components from input to output.
Absolute Temperature Scale
The temperature scale whose origin is the temperature at which all
molecular motion would cease. The unit is the degree Kelvin (oK), which
has the same magnitude as a degree celsius (oC).
Absorptive Device
A circuit or device that absorbs power, i.e., converts incident electrical
energy into heat or some other form of energy, rather than reflecting electrical
energy back to the source.
AC
Alternating current
Acceptor
A material that is intentionally added to a pure semiconductor material
to increase the population of free holes in that semiconductor, resulting
in a net positive charge. A semiconductor that has had acceptor material
added to it is called "p-type."
Active Device
A component that changes the basic character of an electric signal
by amplification, rectification, switching, etc. A device whose output
is dependent upon an external source of power other than the input signal.
Active Device
A component that has gain or operates in a non-linear fashion to change
the basic character of an electric signal by, for example, amplification
or rectification, or a device comprised of such component, for example
a transistor switch. A device whose output is dependent upon an external
source of power other than the input signal.
Active Network
A circuit that produces gain.
Admittance
The ratio of current to voltage, the reciprocal of impedance. The unit
of admittance is the siemens (S). Admittance is typically abbreviated as "y" or "Y."
AGC
(See "automatic gain control").
Alternating Current
The movement of charge carriers in a medium where the direction in
which the carriers move reverses over time, typically with a fixed period,
for example 60 Hz 120 VAC household current.
AM
(See "amplitude modulation").
Amplifier
A circuit or device whose output signal is a faithful version of the
input signal but with increased amplitude, usually specified as voltage
or current.
Amplitude Modulation
The modification of the magnitude of a higher, constant frequency carrier
signal controlled by the amplitude and phase of a lower frequency baseband
or audio signal.
AMPS
Advanced Mobile Phone System. The original American standard for analog
wireless phone systems, used primarily in North America, Latin America,
Australia and parts of Russia and Asia.
Angstrom
Unit of distance equal to 10-10 (10E-10) meter. The symbol for the
angstrom is Å.
Antenna
A structure that is intended to radiate electromagnetic waves into
or collect electromagnetic energy from space.
Antistatic
Of or pertaining to the ability to either prevent the accumulation
of or to enable the dissipation of static charge.
ATM
Asynchronous Transfer Mode. A communication protocol for broadband
transmission of voice, data and video.
Attenuation
The degree to which an input signal is reduced in amplitude at the
output of a circuit or device. Attenuation is typically expressed in dB.
Attenuator
A two port circuit or device that reduces the amplitude of an input
signal by a desired amount typically expressed in decibels (dB). Attenuators
may be comprised of fixed resistors. PIN diodes or FET's, or combinations
of these.
Atto
A prefix that indicates a factor of 10-18, abbreviated as "a."
Attoboy
An amount consisting of 10-10 boys.
Automatic Gain Control
A feedback system that changes the gain of an amplifier or the attenuation
of an attenuator in response to variations in magnitude of the input signal,
thereby maintaining the output signal of the system at a constant magnitude.
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