18WuD2x

1. To excite (i.e., to supply with input-signal
current, power, or voltage) (see DRIVING CUR-
RENT, DRIVING POWER, and DRIVING VOLTdress
• driver element 213
capacitance, best suppression of oscillation, minimum
pickup, etc.).
dressed contact A contact having a permanently
attached locking spring member.
drift 1. Within a conductor or semiconductor, the
controlled, directed movement of charge carriers
resulting from an applied electric field. 2. A usually
gradual and undesirable change in a quantity,
such as current, as a result of a disturbing
factor, such as temperature or age.
drift current In a semiconductor, the current resulting
from a flow of charge carriers in the presence
of an electric field. The charge carriers are
electrons in n-type material and holes in p-type
material.
drift field The inherent internal electric field of a
DRIFT-FIELD TRANSISTOR.
drift-field transistor An alloy-junction, bipolar,
radio-frequency (RF) transistor for which the impurity
concentration is graded from high on the
emitter side of the base wafer to low on the collector
side. This creates an internal drift field that
accelerates current carriers and raises the upper
frequency limit of the transistor.
drift-matched components Active or passive
components that have been closely matched in
terms of the drift of one or more parameters, with
respect to time, temperature, etc.
drift mobility For current carriers in a semiconductor,
the average drift velocity per unit electric
field.
drift space 1. In a vacuum tube, a space that is
nearly free of alternating-current (ac) fields from
the outside, and in which the repositioning of
electrons is governed by the space-charge forces
and the velocity distribution of the electrons. 2.
In a Klystron, the space between buncher and
catcher cavities in which there is no field.
drift speed The average velocity of charge carriers
moving through a medium.
drift transistor See DRIFT-FIELD TRANSISTOR.
drift velocity The net velocity of a charged particle
(electron, hole, or ion) in the direction of the field
applied to the conducting medium.
drift voltage The usually gradual change in voltage
resulting from such causes as internal heating.
Also called voltage drift.
drip loop In a transmission line for an antenna or
power service, a loop near the point of entry to the
building for the purpose of allowing condensation
or rain water to drip off.
drip-proof motor A motor with ventilating apertures
arranged so that moisture and particles
cannot enter the machine.
drip-tight enclosure A housing designed to prevent
entry of rain, snow, and dust; it also prevents
accidental contact with the enclosed
apparatus or machinery.
drive
AGE). 2. Input-signal excitation (see DRIVING
CURRENT, DRIVING POWER, and DRIVING
VOLTAGE). 3. A device that moves a recording
medium (e.g., tape drive and diskette drive). 4.
The transmission of mechanical energy from one
place to another (e.g., motor drive).
drive array A set of two or more hard-disk drives in
a computer system. They function together to
minimize the possibility of data loss. Such a system
can also increase the amount of fast-access
data storage.
drive belt A continuous belt used to transmit mechanical
energy from a driving pulley to a driven
pulley.
drive circuit 1. A circuit used to provide the excitation
to a motor. 2. An amplifier that supplies
drive to a more powerful amplifier.
drive control In a television receiver, the potentiometer
used to adjust the ratio of horizontal
pulse amplitude to the level of the linear portion
of the sawtooth scanning-current wave.
driven element In a multielement antenna, an element
to which electromagnetic energy is fed directly,
as opposed to a PARASITIC ELEMENT,
which is excited by a nearby radiator element.
driven-element directive antenna A multielement
directional antenna whose elements are
driven from the feed line (i.e., no element is parasitic).
Compare PARASITIC-ELEMENT DIREC-
TIVE ANTENNA.
driven multivibrator A multivibrator whose operation
or frequency is controlled by an external
synchronizing or triggering voltage. Compare
FREE-RUNNING MULTIVIBRATOR.
driven single sweep A single oscilloscope sweep
that is initiated by the signal under observation.
drive pattern A pattern of interference in a facsimile
system that is caused by improper synchronization
of the recording spot.
driven sweep An oscilloscope sweep that is initiated
by the signal under observation.
drive pin A pin used to prevent a record from slipping
on the rotating turntable of a recorder or reproducer.
It is similar to, and located near, the
center pin of the turntable.
drive pulse In digital computer operations, a pulse
that magnetizes a cell in a memory bank.
driver 1. A device that supplies a useful amount of
signal energy to another device to ensure its
proper operation (e.g., a current driver for a magnetic-core
memory, an oscillator driving a loudspeaker).
2. A power amplifier stage that supplies
signal power to a higher-powered amplifier stage.
3. In a digital computer, a stage that increases
the output current or power of another stage
(e.g., a clock driver). 4. The cone and magnet of a
dynamic speaker.
driver element In a multielement directive antenna,
the element excited directly by the feeder,
the other elements (directors and reflectors) being
parasitic.