18WuD2x

differentiate • diffused sound 187
differentiate 1. To produce an output signal, the
instantaneous amplitude of which is proportional
to the instantaneous rate of change of the input
amplitude. 2. To determine the derivative of a
mathematical function.
differentiating circuit See DIFFERENTIATING
NETWORK.
differentiating network A four-terminal resistance-capacitance
(RC) network whose output
voltage is the derivative of the input voltage, with
respect to time. Compare INTEGRATING NET-
WORK.
differentiation 1. The processing of an input signal
to create an output signal whose voltage
waveform represents the derivative, with respect
to time, of the input voltage waveform. 2. The process
of computing a mathematical derivative.
differentiator 1. See DIFFERENTIATING NET-
WORK. 2. An operational amplifier whose output
waveform is the mathematical derivative of the
input waveform.
E i
C
R
A V
differentiator, 2
E o = −RC (dE i /dt)
diffracted wave A wave or ray of energy undergoing
DIFFRACTION.
diffraction 1. Interference of one part of an energy
beam with another part when the beam is deflected
along two or more paths having different
lengths. When this happens with visible light,
dark and light bands or colored bands appear.
This effect is responsible for the rainbow-like appearance
of light reflected from the surface of a
compact disc. 2. The bending of electromagnetic
waves around an object. This effect explains why
radio signals can propagate around large obstructions,
such as buildings and hills. The effect
becomes more pronounced as the wavelength increases
(the frequency decreases). 3. The bending
of acoustic waves around an object. This effect
explains why sound propagates around large obstructions,
such as buildings. The effect becomes
more pronounced as the wavelength increases
(the frequency decreases).
diffraction grating A transparent plate containing
thousands of parallel lines or grooves spaced extremely
close together. Light passing through the
slits between the lines produces a rainbow spectrum
as a result of DIFFRACTION.
diffraction spectrum 1. The spectrum produced
in visible light by a diffraction grating. 2. The dis-
tribution of energy at various frequencies, produced
by diffraction of electromagnetic waves. 3.
The distribution of energy at various frequencies,
produced by diffraction of acoustic waves.
diffractometer An instrument for measuring the
diffraction of radiation, such as light or X-rays.
diffuse 1. To produce or cause DIFFUSION. 2. Energy
that is diffused.
diffused-alloy transistor See DRIFT-FIELD TRAN-
SISTOR.
diffused-base transistor A bipolar transistor in
which the base region has been diffused into the
semiconductor wafer. Also see DIFFUSED JUNC-
TION.
diffused device A semiconductor device in which
the junction is produced by diffusion (see DIFFU-
SION, 1). Examples: DIFFUSED-BASE TRANSIS-
TOR, DIFFUSED DIODE, DIFFUSED-JUNCTION
RECTIFIER, and DIFFUSED-MESA TRANSIS-
TOR.
diffused diode A semiconductor diode having a
diffused junction.
diffused-emitter-and-base transistor A transistor
in which n and p materials both have been diffused
into the semiconductor wafer to provide
emitter and base junctions. Also see DIFFUSION,
1 and DIFFUSED TRANSISTOR.
diffused junction In a semiconductor device, a pn
junction formed by diffusing a gas into a semiconductor
at a high temperature that is below the
melting point of the semiconductor. Typically, a
gas containing an n-type impurity is diffused into
p-type semiconductor material. Compare ALLOY
JUNCTION.
diffused-junction rectifier A semiconductor rectifier
using a diffused junction.
diffused-junction transistor See DIFFUSED-
BASE TRANSISTOR, DIFFUSED-MESA TRAN-
SISTOR, and DIFFUSED TRANSISTOR.
diffused-layer resistor In an integrated circuit, a
resistor produced by diffusing a suitable material
into the substrate.
diffused-mesa transistor A transistor whose base
is a n-type layer diffused into a p-type wafer (the
remaining p-type material serving as the collector);
its emitter is a small p-type area diffused
into or alloyed with the n-layer. Unwanted diffused
portions are etched away, leaving the transistor
in a mesa shape.
diffused planar transistor A diffused transistor in
which emitter, base, and collector electrodes are
exposed at the face of the wafer, which has an oxide
layer to forestall leakage between surface electrodes.
diffused resistor See DIFFUSED-LAYER RESIS-
TOR.
diffused sound 1. Sound distributed so that its
energy flux is the same at all points. 2. Sound
whose source is difficult to locate or seems to
shift, as that heard from out-of-phase stereo
channels.