Page 235 - Electrical Engineering Dictionary

DQE See detective quantum efficiency. drift (1) movement of free carriers in a
semiconductor due to the electric field.
DRA See dielectric resonator antenna. (2) the relatively uninpaired fluctuation
of adaptive filter coefficients in the direc-
drain terminal of an FET (usually identi- tion of least sensitivity along the eigenvector
cal in structure to the source) to which elec- corresponding to the minimum eigenvalue is
known as coefficient drift.
trons flow. Electrons in the FET channel flow
down the drain, and current flow is defined as Coefficient drift can be a problem if this
the negative direction of electron movement, eigenvalue gets very small, as coefficients
since electrons are negative. In p-channel can drift out of the allowed region. Also
FETs, current flows from source to drain. In important as random, often temperature-
n-channel FETs, current flows from drain to induced, fluctuations in the output levels of
source. The drain is usually considered to be DC amplifiers.
the metal contact at the surface of the die.
drift chamber a series of chambers used
drain conductance the increase in drain to detect particle trajectories. They are simi-
current when the magnitude of the applied lar to multi-wire proportional chambers, ex-
FET drain-to-source voltage is increased. cept the wire spacing is increased. The cor-
Mathematically, the derivative of drain cur- relation between the position of an ionized
rent with respect to drain voltage. track produced by a charged particle and the
time of appearance of an electric pulse at the
wire is used to measure the distance of the
drain saturation current the drain-to-
trajectory from the wires.
source current flow through the JFET under
the conditions that V GS = 0 and | V DS |>|
V P | such that the JFET is operating in the drift space space where electrons move
active or saturated region. due only to their inertia.

drain-source leakage the current flowing drip-proof machine a machine with ven-
in the channel of a MOSFET when its gate tilating openings constructed in such a way
and source are shorted together. The mag- that drops of liquid or solid particles falling
nitude of the leakage current is strongly in- on it, at an angle less than 15 degrees from
fluenced by the applied drain-source voltage, the vertical, can enter the machine neither
the gate length and substrate doping concen- directly nor by striking on it, run along a hor-
tration. izontal or inwardly inclined surface.

drain-to-source voltage (VDS) poten- drive circuit a circuit that produces gate
tial difference between the FET drain and trigger pulses, of desired level and timing, to
source terminals, this voltage determines the turn on and off active switches (just turn on
device operational region and limits the out- for natural-commutated switches) in switch-
put power. For an n-channel device this volt- ing circuits.
age is normally positive, and negative for a
p-channel device. Magnitudes usually range driving-point admittance the admittance
up to as high as 10 V for a low noise device measured at the antenna terminals when the
and much higher for power devices. antenna is in free space (not loaded).

DRAM See dynamic random access DRO See dielectric resonator (stabled)
memory. oscillator.

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2000 by CRC Press LLC