Page 151 - Electrical Engineering Dictionary

common emitter amplifier a single- common-channel interoffice signaling
transistor BJT amplifier in which the input the use of a special network, dedicated to sig-
signal is applied to the base terminal, the out- naling, to establish a path through a commu-
put is taken from the collector terminal, and nication network, which is dedicated to the
theemitterterminalisconnectedtoaconstant transfer of user information.
voltage.
common-mode coupling pick-up from
an electromagnetic field that induces a
common gate amplifier a single-
change in potential on both signal leads of
transistor FET amplifier in which the input
equal magnitude and phase relative to the
signal is applied to the source terminal, the
ground reference potential.
output is taken from the drain terminal, and
the gate terminal is connected to a constant
communication link a point-to-point
voltage.
communication system that typically in-
volves a single information source and a sin-
common mode gain for a differential gle user. This is in contrast to a communica-
amplifier, the ratio of the output signal am- tions network, which usually involves many
plitude to the amplitude of a signal applied sources and many users.
to both the amplifier input terminals (in com-
mon). For an ideal differential amplifier, the communication theory See information
common mode gain would be zero; the devi- theory.
ation of a real differential amplifier from the
ideal is characterized by the common mode community-antenna television (CATV)
rejection ratio (CMRR). a television receiving and distribution system
in which signals from television stations and
common mode noise undesired electri- sometimesFMstationsarereceivedbyanten-
cal signals in lines that are equal in amplitude nas, amplified, and then distributed to com-
and phase with respect to a reference ground. munity subscribers via coaxial or fiber-optic
Common mode voltages and currents can be cable. The system is known as cable TV.
generated by power electronic switching cir-
cuits and can interfere with control or other commutating inductance in switched
electronic equipment. Common mode cur- circuits (converters, inverters, etc.), the in-
rents will also sum into neutrals and ground- ductance that is in series with the switching
ing conductors, which may cause sensitive elements during the process of commutation
fault current detection relays to trip. from one topological state to another. This
inductance results in noninstantaneous com-
mutation due to the fact that current in an
common mode rejection ratio (CMRR)
inductor cannot change instantaneously.
a measure of quality of an amplifier with dif-
ferential inputs, defined as the ratio between
commutating pole See interpole.
the common-mode gain and the differential
gain.
commutating winding See interpole.

common source amplifier a single- commutation the process by which al-
transistor FET amplifier in which the input ternating current in the rotating coil of a DC
signal is applied to the gate terminal, the out- machine is converted to unidirectional cur-
put is taken from the drain terminal, and the rent. Commutation is accomplished via a
source terminal is connected to a constant set of stationary electrical contacts (brushes)
voltage. sliding over multiple, shaft-mounted electri-

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2000 by CRC Press LLC