Three terminal device used to
hold the output voltage of a
power supply constant over a
wide range of load variations.
IGFET
Insulated gate field effect
transistor. Another name for a "MOSFET."
impedance
(Z) Measured in ohms it is the
total opposition to the flow of
current offered by a circuit.
Impedance consists of the vector
sum of resistance and reactance.
impedance coupling
Coupling of two signal amplifier
circuits through the use of an
impedance such as a inductor.
impedance matching
Matching the output impedance of
a source to the input impedance
of a load to attain maximum
power transfer.
incandescence
State of a material when heated
to the point where it emits
light. (red hot or white hot).
induced voltage
Voltage generated in a conductor
when subjected to a moving
magnetic field.
inductance
Property of a circuit to oppose
a change in current. The moving
magnetic field produced by a
change in current causes an
induced voltage to oppose the
original change.
inductive circuit
Circuit having greater inductive
reactance than capacitive
reactance.
inductive reactance
Opposition to the flow of AC
current produced by an inductor.
Measured in Ohms and varies in
direct proportion to frequency.
inductor
Length of conductor used to
introduce inductance into a
circuit. The conductor is
usually wound into a coil to
concentrate the magnetic lines
of force and maximize the
inductance. While any conductor
has inductance, in common usage
the term inductor usually refers
to a coil.
infrared
Electromagnetic heat radiation
whose frequencies are above the
microwave frequency band and
below red in the visible band.
inhibit
To stop an action or block data
from passing.
in phase
When two or more waves of the
same frequency have their
positive and negative peaks
occurring at the same time.
input impedance
Opposition to the flow of signal
current at the input of a
circuit or load.
insulated
When a non conducting material
is used to isolate conducting
materials from one another.
insulating material
Material that will prevent the
flow of current due to its
chemical composition.
insulation resistance
Resistance of insulating
material. The greater the
insulation resistance, the
better the insulation.
integrated
When two or more components are
combined into a circuit and then
incorporated into a single
package.
integrator
A device that approximates and
whose output is proportional to
an integral of the input signal.
A low pass filter.
intermediate frequency
amplifier
In a superheterodyne radio it
amplifies a fixed frequency
lower than the received radio
frequency and higher than the
audio frequency.
intermittent
A fault occurring at random
intervals of time. Intermittent
problems are often difficult to
locate because of the random
nature. They often don't occur
when the technician is present.
internal resistance
Every source has some resistance
in series with the output
current. When current is drawn
from the source some power is
lost due to the voltage drop
across the internal resistance.
Usually called output impedance
or output resistance.
intrinsic material
A semiconductor material with
electrical properties
essentially characteristic of
ideal pure crystal. Essentially
silicon or germanium crystal
with no measurable impurities.
intrinsic stand-off ratio
A unijunction transistor (UJT)
rating used to determine the
firing potential of the device.
inverting amplifier
An amplifier that has a 180°
phase shift from input to
output.
inverting input
In an operational amplifier (op
amp) the input that is marked
with a minus sign. A signal
applied at the inverting input
will be given 180° phase shift
between input and output.
ion
An atom with fewer electrons in
orbit than the number of protons
in the nucleus is a positive
ion. An atom with a greater
number of electrons in orbit
than the number of protons in
the nucleus is a negative ion.
ionized
Atoms become ionized when they
gain or lose a valence electron.
