18WuD2x

118 class-A amplifier • click method
Freq.
adj. {
Clapp oscillator
complete ac driving-voltage cycle. The input signal
never drives the device into the nonlinear portion
of the characteristic curve.
class-AB amplifier Either a CLASS-AB 1 AMPLI-
FIER or a CLASS-AB 2 AMPLIFIER.
class-AB 1 amplifier An amplifier whose bias is adjusted
to a level between that of a class-A amplifier
and that of a class-AB 2 amplifier. Output
electrode current flows during the entire ac driving-voltage
cycle. The input signal drives the
device into the nonlinear portion of the
characteristic curve during part of the cycle.
class-AB 2 amplifier An amplifier whose bias is adjusted
to a level between that of a class-AB 1 amplifier
and that of a class-B amplifier. Output
electrode current flows during more than 50 percent,
but less than 100 percent, of the input signal
cycle.
class-AB modulator A modulator whose output
stage is a class-AB 1 or class-AB 2 amplifier.
class-A modulator A circuit for obtaining amplitude-modulated
signals; essentially a class-A amplifier
with two inputs, one for the carrier and the
other for the modulating signal.
class-A operation The operation of a transistor,
field-effect transistor, or vacuum tube, in which
the collector, drain, or plate current flows during
the entire signal cycle.
class-B amplifier An amplifier whose bias is adjusted
to operate at the cutoff point in the characteristic
curve. Output current flows during
approximately 50 percent of the input signal cycle.
Efficiency is higher than that of a class-A amplifier.
class-B modulator A push-pull modulator whose
output stage is a class-B amplifier.
class-B operation The operation of a transistor,
field-effect transistor, or vacuum tube, in which
the collector, drain, or plate current flows for approximately
half the signal cycle.
+
Out
class-C amplifier An amplifier whose input-electrode
bias is adjusted for operation at a point
considerably beyond cutoff. Output current flows
during less than half of the input signal cycle.
Such an amplifier requires comparatively high
driving power, but is capable of excellent efficiency.
Commonly used in continuous-wave
(CW), amplitude-modulated (AM), and frequencymodulated
(FM) radio transmitters.
class-C operation The operation of a transistor,
field-effect transistor, or vacuum tube, in which
the collector, drain, or plate current flows for significantly
less than half the signal cycle.
class-D telephone A telephone restricted to use by
emergency services, such as fire departments
and guard alarm installations.
classical electron radius Abbreviated r e . The
quantity expressed as e 2 /(m e c 2 ), where e is the
electron’s charge in electrostatic units, m e is its
rest mass, and c is the speed of light. The value
r e is equal to approximately 2.82 × 10 –13 cm or
2.82 × 10 –15 m.
clean room A room for the assembly or testing of
critical electronic equipment. The term is derived
from the extraordinary steps taken to remove
dust and other contaminating agents. The personnel
wear carefully cleaned garments (or disposable
clothing), gloves, caps, and masks; in
some situations, they are required to walk between
ceiling and floor ducts of a vacuum system
upon entering the room.
cleanup process In the process of electron tube
evacuation, a technique used to remove residual
and occluded gases from the vacuum apparatus
and from the device being evacuated.
clear 1. In computer operations, to restore a
switching element (e.g., a flip-flop) or a memory
element to its standard (e.g., zero) state. 2. In
computer practice, an asynchronous input.
clearance The distance between two live terminals,
or between one live terminal and ground.
clear band In optical character recognition, the
part of a document that must remain unprinted.
clear channel 1. A channel in the standard amplitude-modulation
(AM) broadcast band that is designated
to only one station within the area covered
by the signal from that station. 2. In television
broadcasting, a channel for which there are no restrictions
on the nature of the programming.
clear memory A function in a calculator or small
computer that erases the contents of the memory.
clear raster The raster on the screen of a television
picture tube in the absence of a signal, noise, or
faulty beam deflection.
cleavage In a crystalline substance, the quality of
splitting along definite planes. Also, a fragment
resulting from such a cleft.
click filter See KEY-CLICK FILTER.
click method An emergency technique for rendering
an electric current audibly detectable, by