- saturation
Condition in which a further increase in one variable
produces no further increase in the resultant effect. In a bipolar
junction transistor, the condition when the emitter to collector voltage
is less than the emitter to base voltage. This condition puts forward
bias on the base to collector junction.
- sawtooth wave
- Repeating waveform that rises from zero to maximum value
linearly drops back to zero and repeats. A ramp waveform.
- scale
- Set of markings used for measurement.
- schematic diagram
- Illustration of an electrical or electronic circuit with the
components represented by their symbols.
- Schmitt trigger
- Circuit to convert a given waveform to a square wave output.
- Schottky diode
- High speed diode that has very little junction capacitance.
Also known as a "hot-carrier diode" or a "surface-barrier diode."
- scientific notation
- Numbers entered as a number from one to ten multiplied by a
power of ten. Example: 8765 = 8.765 × 103.
- secondary
- Output winding of a transformer. Winding that is connected to
a load.
- secondary cell
- Electrolytic cell used to store electricity. Once discharged
may be restored by recharging by putting current through the cell in the
direction opposite to that of discharge current.
- selectivity
- Charistic of a circuit to discriminate between wanted and
unwanted signals.
- self biasing
- Gate bias for a field effect transistor in which source
current through a resistor produces the voltage for gate to source bias.
- self inductance
- Property that causes a counterelectromotive force to be
produced in a conductor when the magnetic field expands or collapses
with a change of current.
- semiconductor
- An element which is neither a good conductor or a good
insulator, but rather lies somewhere between the two. Characterized by a
valence shell containing four electrons. Silicon, germanium and carbon
are the semiconductors most frequently used in electronics.
- series circuit
- Circuit in which the components are connected end to end so
that current has only one path to follow through the circuit.
- series parallel network
- Network that contains components connected in both series and
parallel.
- series resonance
- Condition that occurs in a series LC circuit at the frequency
where inductive reactance equals capacitive reactance. Impedance is
minmum, current is maximum limited only by resistance in the circuit.
- seven segment display
- Device made of several light emitting diodes arranged in a
numeric or alphanumeric pattern. By lighting selected segments numeric
or alphabet characters can be displayed.
- shells or bands
- Orbital path containing a group of electrons having a common
energy level.
- shield
- Metal grounded cover used to protect a wire, component or
piece of equipment from stray magnetic and/or electric fields.
- short circuit
- Also called a short. Low resistance conection between two
points in a circuit typically causing excessive current.
- shunt resistor
- Resistor connected in parallel or in shunt with another
component or circuit.
- signal
- Electrical quantity that conveys information.
- signal to noise ratio
- Ratio of the magnitude of the signal to the magnitude of
noise usually expressed in decibels.
- silicon
- (Si) Non metalic element (atomic number 14) used in pure form
as a semiconductor.
- silicon-controlled rectifier
- (SCR) Three terminal active device that acts as a gated
diode. The gate terminal is used to turn the device on allowing current
to pass from cathode to anode.
- silicon controlled switch
- An SCR with an added terminal called an anode gate. A
positive pulse either at the anode gate or the cathode gate will turn
the device on.
- silicon dioxide
- Glass like material used as the gate insulating material in a
MOSFET.
- silicon transistor
- A bipolar junction transistor using silicon as the
semiconducting material.
- silver
- (Ag) Precious metal that does not easily corrode and is more
conductive than copper.
- silver mica capacitor
- Mica capacitor with silver deposited directly onto the mica
sheets instead of using conductive metal foil.
- silver solder
- Solder composed of silver, copper and zinc. Has a melting
point lower than pure silver, but higher than lead-tin solder.
- simplex
- Communication in only one direction at a time. Example: FAX.
- simulcast
- Broadcasting a program simultaneously in two different forms,
for example a program broadcast in both AM and FM.
- sine
- Sine of an angle of a right angle triangle is equal to the
opposite side divided by the hypotenuse.
- sine wave
- Wave whose amplitude is the sine of a linear function of
time. It is plotted on a graph that plots amplitude against time or
radial degrees relative to the angular rotation of an alternator.
- single in-line package
- Package containing several electronic components (generally
resistors) with a single row of connecting pins.
- single pole double throw
- (SPDT) Three terminal switch in which one terminal can be
connected to either one of the other terminals.
- single pole single throw
- (SPST) Two terminal switch or relay thet can open or close
one circuit.
- single sideband
- (SSB) AM radio communication technique in which the
transmitter suppresses one sideband and therefore transmits only a
single sideband.
- single throw switch
- Switch containing only one set of contacts which can be
either opened or closed.
- sink
- Device such as a load that consumes power or conducts away
heat.
- sintering
- Process of bonding either a metal or powder by cold pressing
it into a desired shape and then heating to form a strong cohesive body.
- sinusoidal
- Varying in proportion to the sine of an angle or time
function. AC voltage in which the instantaneous value is equal to the
sine of the phase angle times the peak value.
- SIP
- Abbreviation for "single in-line package."
- skin effect
- Tendancy of high-frequency (rf) currents to flow near the
surface layer of a conductor.
- slew rate
- The maximum rate at which the output voltage of an op-amp can
change.
- slide switch
- Switch having a sliding button, bar or knob.
- slow acting relay
- Slow operating relay that when energized may not pull up the
armature for several seconds.
- slow-blow fuse
- Fust that can withstand a heavy current (up to ten times its
rated value) for a small period of time before it opens.
- snap switch
- Switch containing a spring under tension or compression that
causes the contacts to come together suddenly when activated.
- SNR
- Abbreviation for "signal to noise ratio."
- soft magnetic material
- Ferromagnetic material that is easily demagnetized.
- software
- Program of instructions that directs the operation of a
computer.
- solar cell
- Photovoltaic cell that converts light into electric energy.
Especially useful as a power source for space vehicles.
- solder
- Metallic alloy used to join two metal surfaces.
- soldering
- Process of joining two metallic surfaces to make an
electrical contact by melting solder (usually tin and lead) across them.
- soldering iron
- Tool with an internal heating element used to heat surfaces
being soldered to the point where the solder becomes molten.
- solenoid
- An air core coil. Equipped with a movable iron core the
solenoid will produce motion. As a result of current through the coil
the iron core is pulled into the center of the winding. When the coil is
deenergized, a spring pulls the movable core away from the center of the
winding. Machanical devices connected to the movable core are made to
move as a result of current through the coil. Example: Electric door
locks on some automobiles.
- solid conductor
- Conductor having a single solid wire instead of strands of
fine wire twisted together.
- solid state
- Pertaining to circuits where signals pass through solid
semiconductor material such as transistors and diodes as opposed to
vacuum tubes where signals pass through a vacuum.
- sonar
- Acronym for "sound navigation and ranging." A system using
reflected sound waves to determine the position of some target.
- sonic
- Pertaining to sound.
- sound wave
- Pressure waves propagated through air or other plastic media.
Sound waves are generally audible to the human ear if the frequency is
between approximately 20 and 20,000 vibrations per second. (hertz)
- source
- Device that provides signal power or energy to a load.
- source follower
- FET amplifier in which signal is applied between gate and
drain with output taken between source and drain. Also called "common
drain."
- source impedance
- Impedance through which output current is taken from a
source.
- south pole
- Pole of a magnet into which magnetic lines of force are
assumed to enter.
- spark
- Momentary discharge of electrical energy due to ionization of
air or other dialectric material separating two charges.
- SPDT
- Single pole double throw.
- speaker
- Also called "loudspeaker." Transducer that converts
electrical energy into mechanical energy at audio frequencies.
- spectrum
- Arrangement or display of light or other forms of
electromagnetic radiation separated according to wavelength, energy or
some other property.
- spectrum analyzer
- Instrument used to display the frequency domain of a waveform
plotting amplitude against frequency.
- speed-up capacitor
- Capacitor added to the base circuit of a BJT switching
circuit to improve the switching time of the device.
- SPST
- Abbreviation for "single pole single throw."
- square wave
- Wave that alternates between two fixed values for an equal
amount of time.
- static
- Crackling noise heard on AM radio receivers. Caused by
electric storms or electric devices.
- static electricity
- Stationary electric charges.
- static reverse current
- Reverse current through a zener diode when the reverse
voltage across the diode is less than the zener voltage rating of the
device.
- stator
- Stationary part of some rotary device such as a variable
capacitor.
- step-down transformer
- Transformer in which the output AC voltage is less than the
input AC voltage.
- step-up transformer
- Transformer in which the output AC voltage is greater than
the input AC voltage.
- stereo sound
- System in which reproduced sound is delivered through two or
more channels to give a sense of direction to the source.
- stop band
- Range of frequencies outside the pass band of a tuned
amplifier.
- storage time
- In a BJT switching circuit, it is the time required for
collector current to drop from 100% to 90% of its maximum value.
- stranded conductor
- Conductor composed of a group of strands of wire twisted
together.
- stray capacitance
- Undesirable capacitance that exists between two conductors
such as two leads or one lead and a metal chassis.
- subassembly
- Components contained in a unit for convenience in assembling
or servicing equipment.
- subatomic
- Particles such as electrons, protons and neutrons that are
smaller than atoms.
- substrate
- Mechanical insulating support upon which a device is
fabricated.
- summing amplifier
- An op-amp circuit whose output is proportional to the sum of
its instantaneous voltages.
- superconductor
- Metal such as lead or niobium that, when cooled to within a
few degrees of absolute zero, can conduct current with no resistance.
- superheterodyne receiver
- Radio receiver that converts all radio frequencies to a fixed
intermediate frequency to maximize gain and bandwidth before
demodulation.
- super high frequency
- (SHF) Frequency band between 3 GHz and 30 GHz. So desiganted
by Federal Communications Comission (FCC).
- superposition theorem
- Theorem designed to simplify networks containing two or more
sources. It states that in a network containing more than one source,
the current at any one point is equal to the algebraic sum of the
currents produced by each source acting separately.
- supply voltage
- Voltage provided by a power source.
- surface-barrier diode
- (Schottky diode)High speed diode that has very little
junction capacitance. Also known as a "hot-carrier diode."
- surface leakage current
- Diode reverse current that passes along the surface of the
semiconductor materials.
- surge current
- High charging current that flows into a power supply filter
capacitor as the power is first turned on.
- sweep generator
- Test instrument designed to produce a voltage that
continously varies in frequency over a band of frequencies. Used as a
souce to display frequency response of a circuit on an oscilloscope.
- switch
- Electrical device having two states, on (closed) or off
(open). Ideally having zero impedance when closed and infinite impedance
when open.
- switching transistor
- transistor designed to change rapidly between saturation and
cut-off.
- synchronization
- Also called sync. Precise matching of two waves or functions.
- synchronous
- Two or more signals in step or in phase.
- sync pulse
- Pulse used as a reference for synchronization.
- system
- Combination of several pieces of equipment to perform in a
particular manner.
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