18WuD2x

Brewster angle • bridge-type meter 85
Brewster angle From BREWSTER’S LAW, the polarizing
angle at which the reflected and refracted
rays of incident light are perpendicular to each
other.
Brewster’s law (Sir David Brewster, 1781–1868).
For any dielectric reflector, the relationship in
which the refractive index is equal to the tangent
of the polarizing angle.
bridge 1. A network, usually consisting of four
branches, connected so that an input signal can
be applied between two opposite points and the
output taken between the other two opposite
points. When the component values are in a certain
ratio, the voltage between the output points
is zero, and the bridge is said to be balanced or
set to null. 2. A circuit such as that described in
(1) used for electrical measurements. 3. An audio
or servo amplification system in which the load is
driven from two outputs having opposite polarity,
neither of which are at ground potential. 4. A
communications path between or among two or
more networks. This allows the subscribers in
any network to obtain data from, or send data to,
any other network, in effect creating a network of
networks.
bridge balance control A potentiometer, variable
capacitor, or variable inductor that is used to adjust
a bridge circuit to balance.
bridge-connected amplifier 1. A dc amplifier
stage in which the transistors and resistors are
connected in a four-arm bridge circuit, with respect
to dc. When the bridge is initially balanced,
all dc is eliminated in the output load. The input
signal unbalances the bridge, which results in an
amplified output signal in the load. 2. An amplifier
pair having opposing outputs across which a
load can be bridged to obtain twice the power output
of either amplifier alone.
bridged differentiator See HALL NETWORK.
bridge detector The output-indicating device
(e.g., meter, oscilloscope, or headphones) that
indicates whether a bridge is balanced or unbalanced.
Also called null detector or null indicator.
bridged integrator A null network that consists of
a two-stage resistance-capacitance (RC) integrator
circuit bridged by a capacitor. This network
produces a shallow null at a single frequency determined
by the R and C values in the integrator.
Compare HALL NETWORK.
bridged-tee attenuator An attenuator consisting
of a tee section, between the input and output of
which is bridged a single-series arm.
bridged-tee circuit Any circuit (of resistors, capacitors,
inductors, or a combination of these)
that consists of a tee section, bridged by a singleseries
section, from input to output.
bridged-tee null network A bridged-tee circuit of
resistance (R) and capacitance (C), proportioned
so that at some setting of the R and C values, the
output of the circuit is zero.
Input
C1
R1 R2 R3
C2
C 1 = C 2 = C 3
R 1 = R 2 = R 3
f null =
1.732
2πR 1 C 1
bridged-tee oscillator A low-distortion oscillator
circuit whose frequency is determined by a
bridged-tee null network inserted into the negative-feedback
path of the circuit.
bridge feedback A combination of current feedback
and voltage feedback around an amplifier
circuit. It is so called because, in the feedback circuit,
the resistors and the output resistance of
the amplifier form a four-arm bridge.
bridge generator The power source (e.g., a battery
or oscillator) that supplies the signal to a BRIDGE
used for electrical measurements.
bridge indicator See BRIDGE DETECTOR.
bridge oscillator See BRIDGE GENERATOR.
bridge rectifier A full-wave rectifier circuit in
which four rectifying diodes are connected in a
bridge configuration. Each half-cycle of ac input
is rectified by a pair of diodes in opposite quarters
of the bridge and in series with each other. The
bridge does not require a transformer with a
center-tapped secondary, as does the FULL-
WAVE, CENTER-TAP RECTIFIER circuit.
bridge source See BRIDGE GENERATOR.
bridge-type meter A frequency-sensitive bridge
(such as the Wien bridge) that can be used to
measure audio frequency. Because the bridge
can be balanced at only one frequency at a time,
C3
bridged integrator
Output