18WuD2x

256 emissivity • empirical design
source at a particular temperature, and W 2 is the
energy emitted by a blackbody (i.e., a theoretically
perfect radiator) at the same temperature.
emittance For an energy-radiating source, the radiated
power per unit area of radiating surface.
emitted electron An electron that has left an atom
of a material and has escaped into surrounding
space or entered a neighboring material.
emitter 1. A body that discharges particles or
waves (see EMISSION). 2. In a semiconductor device,
the area, region, or element from which current
carriers are injected into the device. In a
transistor symbol, the emitter is that electrode
shown with an arrowhead.
emitter-base junction In a bipolar transistor, the
boundary between base and emitter regions.
emitter bias Emitter current or voltage maintained
to set the operating point of a bipolar transistor.
emitter bulk resistance The portion of the resistance
of the semiconductor material in a transistor
that affects emitter resistance.
emitter-coupled logic A bipolar form of digital
logic, abbreviated ECL.
emitter-coupled multivibrator A two-transistor
multivibrator circuit in which the emitters share
a common resistor.
emitter-coupled phase inverter A transistor
phase inverter in which the out-of-phase component
is taken from the collector and the in-phase
component from the emitter resistor (of the same
transistor). Another transistor is often used to
amplify the in-phase component so that both outputs
are equal in magnitude.
Input
+dc
emitter-coupled phase inverter
Output
Output
emitter current Symbol, I E . The current in the
emitter electrode of a bipolar transistor.
emitter degeneration In a transistor amplifier,
current degeneration obtained by use of an unbypassed
emitter resistor. The arrangement results
in virtually distortion-free amplification at a sacrifice
in voltage gain.
emitter follower A transistor circuit in which the
input signal is applied to the base, and the output
signal is taken from the emitter resistor. Gain is
always less than unity; output impedance is low.
Input
+dc
emitter follower
Output
emitter-input circuit See COMMON-BASE CIR-
CUIT.
emitter junction See EMITTER-BASE JUNCTION.
emitter resistance Symbol, R E . 1. The resistance
of the emitter electrode in a bipolar transistor. 2.
External resistance connected to a transistor’s
emitter terminal.
emitter stabilization In a common-emitter transistor
stage, an emitter resistor that stabilizes the
circuit against temperature variations.
emitter-to-base junction See EMITTER-BASE
JUNCTION.
emitter voltage Symbol, V E . The voltage at the
emitter electrode of a bipolar transistor.
EMP, emp 1. Abbreviation of ELECTROMAGNETIC
PULSE. 2. Abbreviation of electromagnetic power.
emphasis Modification of the amplitude-versusfrequency
output or response of an audio circuit,
for the purpose of optimizing signal intelligibility.
emphasizer An audio-frequency device with a specially
tailored response, intended to maximize intelligibility
of a voice.
Empire cloth Varnished cambric used as an insulating
sheet or tape.
empirical Observable; derived from experimentation.
empirical curve A curve plotted from data acquired
from observations, tests, and calculations,
rather than from mathematical laws or other theory.
empirical design The design of electronic circuits
by cut-and-try methods and, to some extent,