18WuD2x

70 berkelium • biased off
berkelium Symbol, Bk. A radioactive elemental
metal produced artificially. Atomic number, 97.
Atomic weight, 247.
beryllia Formula, Be0. Beryllium oxide, used in
various forms as an insulator and structural element
(as in resistor cores).
beryllium Symbol, Be. An elemental metal. Atomic
number, 4. Atomic weight, 9.01218. Beryllium is
present in various dielectrics and alloys used in
electronic components.
Bessel functions Sophisticated mathematical
functions for dealing with periodic electronic phenomena
in which the waveform often displays
decrement. Also called cylindrical functions.
beta Symbol, β. The current gain of a commonemitter
bipolar transistor stage. It is the ratio of
the induced change of collector current to the applied
change of base current: β = dIC/dIB.
beta circuit The output-input feedback circuit in
an amplifier.
beta cutoff frequency The frequency at which the
current amplification of a bipolar transistor falls
to 70.7% of its low-frequency value.
beta particles Minute radioactive subatomic bits
identical to the electron or positron, and emitted
by some radioactive materials. Also see BETA
RAYS.
beta rays Rays emitted by the nuclei of radioactive
substances, consisting of a stream of beta particles
(i.e., electrons or positrons) that move at velocities
up to 299.8 million meters per second.
Compare ALPHA PARTICLE and GAMMA RAYS.
beta-to-alpha conversion For a bipolar transistor,
the conversion of current amplification expressed
as beta (β) to current amplification expressed as
alpha (α): α = β/(β + 1).
betatron A particle accelerator in which injected
electrons are given extreme velocity by being propelled
in circular paths in a doughnut-shaped
glass container. The term comes from the fact
that high-speed electrons constitute BETA PAR-
TICLES.
beta videocassette recorder The earliest scheme
for videocassette recording, developed by Sony
corporation in the 1970s. Compare VHS videocassette
recorder.
beta zinc silicate phosphor Formula, (Zn0 +
Si0 2 ):Mn. A phosphorescent substance used to
coat the screen of a cathode-ray tube. The fluorescence
is green-yellow.
BeV Abbreviation of billion electronvolts. Also see
ELECTRONVOLT, GEV, MEV, and MILLION
ELECTRONVOLTS. This abbreviation has been
supplanted by the SI (International System of
Units) abbreviation GeV, for GIGAELECTRON-
VOLTS.
bevatron An accelerator (see ACCELERATOR, 1)
similar to the synchrotron, which accelerates
particles to levels greater than 10 GeV.
Beverage antenna (Harold H. Beverage.) A nonresonant,
directional long-wire antenna, erected a
few feet above ground and run in a straight line
for one to several wavelengths. It is generally
used for reception at low and medium frequencies,
the best response is to vertically polarized
signals arriving from one or both directions in
line with the wire. It can be left unterminated for
bidirectional response, or it can be terminated at
its far end by a noninductive resistor of about 600
ohms for a unidirectional response.
beyond-the-horizon propagation See FORWARD
SCATTER.
bezel A faceplate for an electronic instrument,
usually having a fitted rim and cutouts for knobs,
switches, jacks, etc.
BFO Abbreviation of BEAT-FREQUENCY OSCIL-
LATOR.
BG Abbreviation of BIRMINGHAM WIRE GAUGE.
Also abbreviated BWG.
B-H curve A plot showing the B and H properties of
a magnetic material. Magnetizing force H is plotted
along the horizontal axis, and flux density B
is plotted along the vertical axis.
B-H loop See BOX-SHAPED LOOP.
B-H meter Any instrument for displaying or evaluating
the hysteresis loop of a magnetic material.
bhp Abbreviation of brake horsepower.
Bi Symbol for BISMUTH.
bias 1. Any parameter of which the value is set to a
predetermined level to establish a threshold or
operating point. Although it is common to think
of bias currents and bias voltages, other parameters
(e.g., capacitance, resistance, illumination,
magnetic intensity, etc.) can serve as biases. 2. In
a high-fidelity audio system, a circuit in a tape
recorder/player that optimizes performance for a
particular type of recording tape.
bias current A steady, constant current that presets
the operating threshold or operating point
of a circuit or device, such as a transistor,
diode, or magnetic amplifier. Compare BIAS
VOLTAGE.
bias current drift The ratio of a change in input
bias current to a change in ambient temperature,
generally expressed in nanoamperes per degree
Celsius.
bias distortion Distortion caused by operation of a
tube or transistor with incorrect bias so that the
response of the device is nonlinear.
biased diode A diode having a dc voltage applied in
either forward or reverse polarity. Current flows
readily through the forward-biased diode; the reverse-biased
diode appears as an open circuit.
The biased diode is the basis of clippers, limiters,
slicers, and similar circuits.
biased off
In a circuit or device, the state of cutoff
caused by application of a control-electrode bias.
Examples include collector-current cutoff (when
the dc base bias of a bipolar transistor reaches a
critical value), and drain-current cutoff (when the
dc gate bias reaches a critical value in a fieldeffect
transistor).