Page 69 - The Illustrated Dictionary of Electronics

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54 avalanche breakdown • AX.25

mum reverse-bias voltage required to cause this
phenomenon varies among different kinds of
diodes. Some diodes are manufactured to have
precise avalanche voltages. See ZENER DIODE.
avalanche conduction In a semiconductor junc-
tion, the enhanced reverse-bias conduction
caused by a condition of AVALANCHE.
avalanche current The high current that flows
through a semiconductor junction when
AVALANCHE occurs.
avalanche diode See ZENER DIODE.
avalanche impedance The reduced impedance of
a diode during avalanche.
avalanche noise Electrical noise generated in a
junction diode operated at the point at which
avalanche just begins.
avalanche transistor A transistor that operates at
a high value of reverse-bias voltage, causing the average rectified current Abbreviation, I avg . The
pn junction between the emitter and base to con- average value of rectifier output current before fil-
duct because of avalanche breakdown. tering. For a full-wave rectifier with a sine wave
avalanche voltage In a semiconductor P-N junc- input and a resistive load, I avg is equal to the max-
tion, the minimum applied reverse-bias voltage imum current I m multiplied by 0.637.
that produces AVALANCHE BREAKDOWN. average rectified voltage Abbreviation, E avg . The
AVC Abbreviation of automatic volume control. average value of rectifier output voltage before fil-
avdp Abbreviation for Avoirdupois, a weight- tering. For a full-wave rectifier with a sine-wave
measurement scheme that is used in English- input and a resistive load, E avg is maximum volt-
speaking countries and is based on the pound. age E m multiplied by 0.637.
average absolute pulse amplitude The average average value 1. The arithmetic mean of two or more
(disregarding algebraic sign) of the absolute am- quantities. 2. The geometric mean of two or
plitudes of a pulse, taken over the duration of the more quantities. 3. The harmonic mean of two
pulse. or more quantities. 4. In ac operation, the aver-
average brightness The average brilliance of a age current, voltage, or power.
television (TV) picture, cathode-ray-tube (CRT) average voltage Abbreviation, E avg . The average
computer display, or oscilloscope image. value of ac voltage in a circuit. Taking polarity into
average calculating operation The operating time account, this value is zero for a pure sine wave.
considered typical for a computer calculation For other waveforms, it can vary. When polarity is
(i.e., one that is longer than an addition and not considered, the sine-wave value of E avg is equal
shorter than a multiplication); it is frequently to 0.637 times E pk , the peak value of voltage.
taken as the average of nine additions and one avg Abbreviation of average.
multiplication. aviation channels Frequency channels assigned
average current Abbreviation, I avg. The average to the AVIATION SERVICES.
value of alternating current flowing in a circuit. Aviation services The radio-communication ser-
Taking polarity into account, this value is zero for vices used by aeronautical-mobile and radio nav-
a pure sine wave. For other waveforms, it can igation personnel.
vary. When polarity is not considered, the sine- avigation Acronym for aviation navigation. Aircraft
wave value of I avg is equal to 0.637 times I pk, the navigation by means of electronic equipment.
peak value of current; I avg = 0.637 I pk. avionics Acronym for aviation electronics. The de-
average life See MEAN LIFE. sign, production, and application of electronic de-
average noise figure The ratio of the total noise vices and systems for use in aviation, navigation,
output from a circuit to the thermal noise output and astronautics.
at 290 degrees Kelvin. It is usually expressed in Avogadro’s constant (Amedeo Avogadro, 1776–
decibels, with the noise taken at all frequencies. 1856.) Symbol, NA. The number of molecules in a
average power The average value of power in an ac kilogram-molecular weight of any substance; NA
–1
circuit. In a resistive circuit, it is the square of the equals 6.025 × 10 26 (kg-mole) .
effective (rms) current times the resistance; P avg = A voltage The filament voltage in a vacuum-tube
2
(I rms) R (for sine waves). circuit.
average pulse amplitude Also called effective aW Abbreviation of attowatt.
pulse amplitude. The value obtained by integrat- AWG Abbreviation of AMERICAN WIRE GAUGE.
ing the pulse amplitude, with respect to time, AX.25 A signal format used in some digital com-
from the start of the pulse to its end, then divid- munications systems, notably amateur packet ra-
ing this integral by the pulse duration. dio.