18WuD2x

160 current saturation • cutoff frequency
current saturation In the operation of a device
(such as a transistor, saturable reactor, or magnetic
amplifier), the leveling off of current at a
value beyond which no further increase occurs—
even though an input parameter is further increased.
current sense amplifier An amplifier used to increase
the sensitivity of, or to decrease the loading
of, a current-sensing component.
current sensing Sampling a current (e.g., when
the voltage drop across a series resistor is used as
a proportional indication of the current flowing
through the resistor).
current-sensing resistor A low-value resistor inserted
into a circuit primarily for current sensing.
current sensitivity In a current meter or galvanometer,
current (in amperes or fractions
thereof) per scale division.
current-sheet inductance Symbol, L S . The lowfrequency
inductance of a single-layer coil, calculated
with the formula L S = (0.10028 a 2 N 2 )/s,
where L S is in microhenrys, a is the coil radius in
inches, N is the total number of turns, and s is
the coil length in inches.
current shunt 1. A resistor connected in parallel
with a voltmeter to convert it into an ammeter. 2.
A resistor connected in parallel with the input of
a voltage amplifier to make the response of the
amplifier proportional to input-signal current.
current sink A circuit or device through which a
constant current can be maintained.
current-sinking logic A form of bipolar digital
logic. Current flows from one stage to the input of
the stage immediately before.
current-squared meter An ammeter or milliammeter
whose deflection is proportional to the
square of the current.
current-stability factor In a common-base connected
bipolar transistor, the ratio dI E /dI C , where
I E is the emitter current and I C is the collector
current.
current strength The magnitude of electric current
(see CURRENT) (i.e., the number of carriers
flowing past a given point per unit time, expressed
in coulombs per second or in amperes).
current transformer 1. A transformer used to increase
or decrease current flow. A primary-tosecondary
step-up turns ratio reduces the
current; a primary-to-secondary step-down turns
ratio increases the current. 2. A particular transformer
(as in 1) used to change the range of an alternating-current
milliammeter or ammeter.
current vector In a vector diagram, a line with an
arrowhead (vector) showing the magnitude and
phase of a current. Compare VOLTAGE VEC-
TOR.
current-voltage feedback In an amplifier or oscillator,
the process of applying some of the output
current and voltage to the input. This feedback
might be in phase (positive) or out of phase (negative),
with respect to the input.
cursor 1. A marker that indicates the position
where a character can be entered in a video alphanumeric
display. Commonly used in computers
and word processors. 2. The sweeping line on
a radar display. 3. The movable marker on a slide
rule.
curve trace 1. A device that supplies a special
variable test voltage to a component or circuit under
test, at the same time supplying a sweep voltage
to an oscilloscope. The component’s output
voltage is also presented to the oscilloscope. As a
result, the response curve of the component appears
on the oscilloscope screen. 2. A device that
produces a permanent record (photographic or
graphic) of an electrical phenomenon. Also called
OSCILLOGRAPH or RECORDER.
curvilinear trace A trace made on paper with
curved vertical lines. The lines are curved to
match the arc through which the recording pen
swings.
cut-in angle In a semiconductor rectifier circuit, a
phase angle slightly greater than zero degrees, at
which current conduction begins. Compare CUT-
OUT ANGLE.
Cutler antenna A parabolic-dish antenna, in
which the driven element consists of a waveguide
that has two apertures on opposite sides of
a resonant cavity.
Cutler feed An aircraft antenna feed system in
which radio-frequency (RF) energy is fed to the reflector
by a resonant cavity at the end of a waveguide.
Cutler tone control A dual resistance-capacitance
(RC) filter circuit of the general bridged-tee variety.
Variation of the series leg provides adjustable
treble boost; variation of the shunt leg provides
adjustable bass boost.
cutoff 1. The process of reducing some operating
parameter, such as collector current, to zero by
adjusting the bias at the input electrode. 2. The
point on the characteristic curve of an amplifying
device, at which the output current drops to zero
under no-signal conditions. 3. The lowest
frequency at which a waveguide will efficiently
function. 4. The frequency or frequencies corresponding
to the point or points in a filter
response, at which the attenuation is three
decibels greater than the lowest attenuation within
the passband. See also CUTOFF FREQUENCY.
cutoff attenuator A variable, nondissipating attenuator
consisting of a variable length of waveguide
used at a frequency below cutoff.
cutoff bias In a transistor or vacuum-tube circuit,
the value of control-electrode bias that produces
output current cutoff.
cutoff current Symbol, I co . In a transistor, the
small collector current that flows when the emitter
current is zero (common-base circuit) or when
the base current is zero (common-emitter circuit).
cutoff frequency 1. Symbol, f co . The high frequency
at which the current-amplification factor