18WuD2x

178 demand read (write) • depth of discharge
demand read (write) Inputting or outputting data
blocks to or from a central processor, as needed
for processing.
demodulator probe A diode probe that removes
the modulation envelope from an applied amplitude-modulated
signal, and presents the envelope
to a voltmeter or oscilloscope.
demonstrator A device used to show and teach the
way in which a component, circuit, or system operates.
DeMorgan’s theorem A rule of sequential or digital
logic. It states that the negation of (A AND B),
for any two statements A AND B, is equivalent to
NOT A OR NOT B. Also, the negation of (A OR B)
is equivalent, logically, to NOT A AND NOT B.
demultiplexer A circuit or device that separates
the components of a multiplexed signal transmitted
over a channel.
demultiplexing circuit See DEMULTIPLEXER.
denary band A band in which the highest frequency
is 10 times the lowest frequency.
dendrite 1. The branching (tree-like) structure
formed by some materials, such as semiconductors,
as they crystallize. 2. The branching portion
of a nerve cell; hence, the corresponding circuit
element in the electronic model of such a cell.
dendritic growth 1. Dendrite (see DENDRITE, 1).
2. The process of growing long, flat semiconductor
crystals.
dendron See DENDRITE, 2.
dens Abbreviation of DENSITY.
dense binary code A binary representation system,
in which any possible combination of characters
is assigned some correspondent.
densitometer An instrument for measuring the
density of a body.
density 1. Mass per unit volume of a material. 2.
Concentration of charge carriers or of lines of
flux. 3. The number of items per unit volume,
area, distance, or time.
density modulation Modulation of the density,
with respect to time, of electrons in an electron
beam.
Electron beam
(Least) (Most) (Least) (Most) (Least)
density modulation
density of electrons The concentration of electrons
(i.e., the number per unit volume, area, distance,
or time).
density packing A figure indicating the quantity of
bits per inch or per centimeter, stored on a magnetic
tape.
dependent equations Equations that are alike
and have an infinite number of solutions. Compare
INDEPENDENT EQUATIONS and INCON-
SISTENT EQUATIONS.
dependent linearity Linearity (especially in its deviation
from an ideal slope) as a dependent variable.
dependent variable A changing quantity whose
value at any instant is governed by the value at
that instant of another changing quantity (the independent
variable). Compare INDEPENDENT
VARIABLE.
depletion-enhancement-mode MOSFET A metaloxide-semiconductor
field-effect transistor (MOS-
FET) designed for zero gate-bias voltage. An ac
gate signal voltage drives the MOSFET alternately
into the depletion mode (negative signal halfcycle)
and enhancement mode (positive signal
half-cycle). Compare DEPLETION-TYPE MOSFET
and ENHANCEMENT-TYPE MOSFET.
depletion field-effect transistor A field-effect
transistor whose operation is based on the control
of depletion layer width.
depletion layer See BARRIER, 1.
depletion-layer capacitance See JUNCTION CA-
PACITANCE.
depletion-layer rectification Rectification provided
by a semiconductor junction.
depletion-layer transistor A transistor whose action
depends on modulation of current carriers in
a space-charge region (depletion layer).
depletion mode Operation characteristic of the
DEPLETION-TYPE MOSFET.
depletion region See BARRIER, 1.
depletion-type MOSFET A metal-oxide-semiconductor
field-effect transistor (MOSFET) in which
the channel directly under the gate electrode is
narrowed by a negative gate voltage (in an n-
channel device) or by a positive gate voltage (in a
p-channel device).
depolarization 1. In a primary cell, the removal of
the agents that have caused polarization. 2. The
addition of a polarization-inhibiting substance to
the electrolyte of a primary cell.
depolarizer A substance that retards polarization
in an electrochemical cell. An example is the
manganese dioxide used in dry cells.
depolarizing agent See DEPOLARIZER.
deposition The application of a layer of one substance
(usually a metal) to the surface of another
(the substrate), as in evaporation, sputtering,
electroplating, silk-screening, etc.
depth finder See ACOUSTIC DEPTH FINDER.
depth indicator 1. A sounding instrument for determining
the depth of a body of water. 2. On an
ACOUSTIC DEPTH FINDER, the meter that indicates
the depth of water.
depth of cut On a phonograph disk, the depth of
the recorded groove.
depth of discharge Abbreviation, DOD. In a rechargeable
cell or battery, a measure of the extent