A
- A
- Abbreviation for "ampere" a unit of electrical current.
- absorption
- Loss or dissipation of energy as it travels through a medium,
Example: radio waves lose some of their energy as they travel through the
atmosphere.
- AC
- Abbreviation for "Alternating Current"
- acceptor atoms
- Trivalent atoms that accept free electrons from pentavalent atoms.
- AC coupling
- Circuit that passes an AC signal while blocking a DC voltage.
- AC/DC
- Equipment that will operate on either an AC or DC power source.
- AC generator
- Device used to transform mechanical energy into AC electrical power.
- AC load line
- A graph representing all possible combinations of AC output voltage and current
for an amplifier.
- AC power supply
- Power supply that delivers an AC voltage.
- active component
- A component that changes the amplitude of a signal between input and output.
- active filter
- A filter that uses an amplifier in addition to reactive components to pass or reject
selected frequencies.
- active region
- The region of BJT operation between saturation and cutoff used for linear
amplification.
- AC voltage
- A voltage in which the polarity alternates.
- ADC
- Abbreviation for "analog to digital converter"
- Admittance
- (symbol "Y") Measure of how easily AC will flow through a circuit.
Admittance is the reciprocal of impedance and is measured in siemens.
- AF
- Abbreviation for "audio frequency".
- AFC
- Abbreviation for "automatic frequency control".
- AGC
- Abbreviation for "automatic gain control"
- alkaline cell
- A primary cell that delivers more current than a carbon-zinc cell.
Also known as an "alkaline manganese cell".
- alligator clip
- Spring clip on the end of a test lead used to make a temporary connection.
- alpha
- Ratio of collector current to emitter current in a bipolar junction transistor
(BJT). Greek letter alpha "a" is the symbol used.
- alternating current
- An electric current that rises to a maximum in one direction, falls back
to zero and then rises to a maximum in the opposite direction and then repeats.
- alternator
- Name for an AC generator.
- AM
- Abbreviation for "amplitude modulation"
- ammeter
- A meter used to measure current.
- ampere
- Unit of electrical current.
- amplifier
- A circuit that increases the voltage, current, or power of a signal.
- amplitude:
- Magnitude or size of a signal voltage or current.
- analog
- Information represented as continously varying voltage or current rather than in discrete
levels as opposed to digital data varying between two discrete levels.
- anode
- The positive electrode or terminal of a device. The "P" material of a diode.
- antenna, transmitting
- A device that converts an electrical wave into an electromagnetic wave that radiates away from the antenna.
- antenna, receiving
- A device that converts a radiated electromagnetic wave into an electrical wave.
- apparent power
- Power attained in an AC circuit as a product of effective voltage and current which reach their peak at different times.
- arc
- Discharge of electricity through a gas such as lightning discharging through the atmosphere.
- armature:
- The rotating or moving component of a magnetic circuit.
- armstrong oscillator
- An oscillator that uses an isolation transformer to achieve positive feedback from output to input.
- astable multivibrator
- An oscillator that produces a square wave output from a DC voltage.
- atom
- The smallest particle that an element can be broken down into and still maintain its unique identity.
- atomic number
- The number of positive charges or protons in the nucleus of an atom.
- attenuate
- To reduce the amplitude of an action or signal. The opposite of amplification.
- audio
- Relating to frequencies that can be heard by the human ear. Approximately 20 Hz. to 20 kHz.
- autotransformer
- A single winding transformer where the output is taken from taps on the
winding.
- average value
- A value of voltage or current where the area of the wave above the value
equals the area of the wave below the value.
- AVC
- Abbreviation for "automatic volume control"
- avionics
- Aviation electronics.
- AWG
- Abbreviation for "american wire gauge". A gauge that assigns a number value to
the diameter of a wire.
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B
- balanced bridge
- Condition that occurs when a bridge circuit is adjusted to produce
a zero output.
- band-pass filter
- A tuned circuit designed to pass a band of frequencies between
a lower cut-off frequency (f1) and a higher cut-off
frequency (f2). Frequencies above and below the pass
band are heavily attenuated.
- band-stop filter
- A tuned circuit designed to stop frequencies between a lower cut-off
frequency (f1) and a higher cut-off frequency (f2) of
the amplifier while passing all other frequencies.
- bandwidth
- Width of the band of frequencies between the half power points.
- barrier potential
- The natural difference of potential that exists across a forward biased
pn junction.
- base
- The region that lies betwen the emitter and collector of a bipolar junction
transistor (BJT).
- base biasing
- A method of biasing a BJT in which the bias voltage is supplied to the base
by means of a resistor.
- battery
- A DC voltage source containing two or more cells that convert chemical energy
to electrical energy.
- baud
- A unit of signaling speed equal to the number of signal events per second.
Not necessarily the same as bits per second.
- beta
- (b) The ratio of collector current to base current in a bipolar junction
transistor (BJT).
- bias
- A DC voltage applied to a device to control its operation.
- binary
- A number system having only two symbols, 0 and 1. A base 2 number system.
- bipolar junction transistor
- (BJT), A three terminal device in which emitter to collector current is
controlled by base current.
- bistable multivibrator
- A multivibrator with two stable states. An external signal is required to
change the output from one state to the other. Also called a latch.
- bleeder current
- A current drawn continously from a souce. Bleeder current is used to
stabilize the output voltage of a source.
- bode plot
- A graph of gain versus frequency.
- branch current
- The portion of total current flowing in one path of a parallel circuit.
- breakdown voltage
- Voltage at which the breakdown of a dialectric or insulator occurs.
- breakover voltage
- Minimum voltage required to cause a diac to break down and conduct.
- bridge rectifier
- A circuit using four diodes to provide full wave rectification. Converts an AC voltage to a pulsating DC voltage.
- buffer
- An amplifier used to isolate a load from a source.
- bulk resistance
- The natural resistance of a "P" type or "N" type semiconductor material.
- butterworth filter
- A type of active filter characterized by a constant gain (flat response)
across the midband of the circuit and a 20 dB per decade roll-off rate for each
pole contained in the circuit.
- BW
- Abbreviation for bandwidth.
- bypass capacitor
- A capacitor used to provide an AC ground at some point in a circuit.
- byte
- Group of eight binary digits or bits.
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C
- cable
Group of two or more insulated wires.
- CAD
Abbreviation for "computer aided design"
- calibration
To adjust the correct value of a reading by comparison to a standard.
- capacitance
The ability of a capacitor to store an electrical charge. The basic unit of capacitance is the Farad.
- capacitive reactance
The opposition to current flow provided by a capacitor. Capacitive reactance is measured in ohms and varies inversly with frequency.
- capacitor
An electronic component having capacitive reactance.
- capacitor microphone
Microphone whose operation depends on variations in capacitance caused by varying air pressure on the movable plate of a capacitor.
- carbon-film resistor
Device made by depositing a thin carbon film on a ceramic form.
- carbon microphone
Microphone whose operation depends on pressure variation in carbon granules causing a change in resistance.
- carbon resistor
Resistor of fixed value made by mixing carbon granules with a binder which is moulded and then baked.
- cascaded amplifier
An amplifier with two or more stages arranged in a series configuration.
- cascode amplifier
A high frequency amplifier made up of a common-source amplifier with a common-gate amplifier in its drain network.
- cathode
The negative terminal electrode of a device. The "N" material in a junction diode.
- cathode ray tube
(CRT) Vacuum tube used to display data in a visual form. Picture tube of a television or computer terminal.
- cell
Single unit used to convert chemical energy into a DC electrical voltage.
- center frequency
Frequency to which an amplifier is tuned. The frequency half way between the cut-off frequencies of a tuned circuit.
- center tap
Midway connection between the two ends of a winding.
- center tapped rectifier
Circuit that make use of a center tapped transformer and two diodes to provide full wave rectification.
- center tapped transformer
A transformer with a connection at the electrical center of a winding.
- ceramic capacitor
Capacitor in which the dialectric is ceramic.
- charge
Quantity of electrical energy.
- charge current
Current that flows to charge a capacitor or battery when voltage is applied.
- chassis
Metal box or frame into which components are mounted.
- chassis ground
Connection to a chassis.
- chebyshev filter
A type of active filter characterized by high roll-off rates (40 dB per decade per pole) and midband gain that is not constant.
- choke
Inductor used to oppose the flow of alternating current.
- circuit
Interconnection of components to provide an electrical path between two or more components.
- circuit breaker
A protective device used to open a circuit when current exceeds a maximum value. In effect a reusable fuse.
- clamper
A diode circuit used to change the DC level of a waveform without distorting the waveform.
- clapp oscillator
A variation of the Colpitts oscillator. An added capacitor is used to eliminate the effects of stray capacitance on the operation of the basic Colpitts oscillator.
- class A amplifier
A linear amplifier biased so the active device conducts through 360 degrees of the input waveform.
- class B amplifier
An amplifier with two active devices. The active components are biased so that each conducts for approximately 180 degrees of the input waveform cycle.
- class C amplifier
An amplifier in which the active device conducts for less than 180 degrees of the input waveform cycle.
- clipper
A diode circuit used to eliminate part of a waveform
- clipping
Distortion caused by overdriving an amplifier.
- clock
A square waveform used for synchronizing and timing of several circuits.
- closed circuit
Circuit having a complete path for current flow.
- closed-loop gain
Gain of an amplifier when a feedback path is present.
- coaxial cable
Transmission line in which the signal carrying conductor is covered by a dialectric and another conductor.
- coefficient of coupling
The degree of coupling between two circuits. - coercive force
(H) Magnetizing force needed to reduce residual magnetism in a material to zero.
- collector
The semiconductor region in a bipolar junction transistor through which a flow of charge carriers leaves the base region.
- collector characteristic curve
A graph of collector voltage over collector current for a given base current.
- color code
Set of colors used to indicate value of a component.
- colpitts oscillator
An oscillator with a pair of tapped capacitors in the feedback network.
- common-anode display
A multisegment light emitting diode (LED) with a single positive voltage input connection. Separate cathode connections are provided for each individual segment.
- common cathode display
A multisegment light emitting diode (LED) with a single negative voltage input connection. Separate anode connections are provided for each individual segment.
- common base amplifier
A BJT circuit in which the base connection is common to both input and output.
- common collector amplifier
A BJT circuit in which the collector connection is common to both input and output.
- common drain amplifier
A FET circuit in which the drain connection is common to both input and output.
- common emitter amplifier
A BJT circuit in which the emitter connection is common to both input and output.
- common gate amplifier
A FET circuit in which the gate connection is common to both input and output.
- common source amplifier
A FET circuit in which the source connection is common to both input and output.
- common-mode rejection ratio
(CMRR) The ratio of op-amp differential gain to common-mode gain. A measure of an op-amp's ability to reject common-mode signals such as noise.
- common-mode signals
Signals that appear simultaneously at two inputs of an operational amplifier (op-amp). Common mode signals are always equal in amplitude and phase.
- comparitor
An op-amp circuit that compares two inputs and provides a DC output indicating the polarity relationship between the inputs.
- complementary symmetry amplifier
A class B amplifier using matched complementry transistors. Does not require a phase inverter for push-pull output.
- complementry transistors
Two transistors, one NPN and one PNP having near identical charastics. N-channel and P-channel FETs can also be complementry.
- complex numbers
Numbers composed of a real number part and an imaginary number part.
- compliance
The maximum possible peak-to-peak output of an amplifier.
- constant current circuit
Circuit used to maintain constant current to a load having resistance that changes.
- contact
Current carrying part of a switch, relay or connector.
- continuity
Occurs when a complete path for current exists.
- conventional current flow
Concept of current produced by the movement of positive charges towards the negative terminal of a source.
- copper loss
Power lost in transformers, generators, connecting wires and other parts of a circuit due to current flow through the resistance of copper conductors.
- core
Magnetic material within a coil used to concentrate the magnetic field.
- coulomb
Unit of electric charge. A negative coulomb charge consists of 6.24 × 1018 electrons.
- counter electromotive force
(counter emf) Voltage induced into an inductor due to an alternating or pulsating current. Counter emf is always in polarity opposite to that of the applied voltage. Opposing a change of current.
- coupling
To electronically connect two circuits so that signal will pass from one to the other.
- covalent bond
The way some atoms complete their valence shells by sharing valence electrons with neighbouring atoms.
- crossover distortion
Distortion caused by both devices in a class B amplifier being cut-off at the same time.
- crowbar
Circuit used to protect the output of a souce from a short circuited load. Load current is limited to a value the source can deliver without damage.
- CRT
Abbreviation for cathode ray tube.
- crystal
Natural or synthetic piezoelectric or semiconductor material with atoms arranged with some degree of geometric regularity.
- crystal-controlled oscillator
Oscillator that uses a quartz crystal in its feedback path to maintain a stable output frequency.
- current
Measured in amperes, it is the flow of electrons through a conductor. Also know as electron flow.
- current amplifier
Amplifier to increase signal current.
- current divider
Parallel network designed to divide the total current of a circuit
- current feedback
Feedback configuration where a portion of the output current is fed back to the amplifier input.
- current-limiting resistor
Resistor in the path of current flow to control the amount of current drawn by a device.
- current mirror
Term used to describe the fact that DC current through the base circuit of a class B amplifier is approximately equal to the DC collector current.
- cutoff
Condition when an active device is biased such that output current is near zero or beyond zero.
- cutoff frequency
Frequency at which the power gain of an amplifier falls below 50% of maximum.
- cycle
When a repeating wave rises from zero to a positive maximum then back to zero and on to a negative maximum and back to zero it is said to have completed one cycle.
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E
- E-core
Laminated form in the shape of the letter "E", onto which inductors and transformers are wound.
- eddy currents
Currents induced into a conducting core due to the changing magnetic field. Eddy currents produce heat which is a loss of power and lowers the efficiency of an inductor.
- efficiency
The amount of power delivered to the load of an amplifier as a percentage of the power required from the power supply.
- electric charge
Electric energy stored on the surface of a material. Also known as a static charge.
- electric field
A field or force that exists in the space between two different potentials or voltages. Also known as an electrostatic field.
- electricity
Science states that certain particles possess a force field or charge. The charge possessed by an electron is negative while the charge possessed by a proton is positive. Electricity can be divided into two groups, static and dynamic. Static electricty deals with charges at rest and dynamic electricity deals with charges in motion.
- electric polarization
A displacement of bound charges in a dielectric when placed in an electric field.
- electroacoustic transducer
Device that produces an energy transfer from electric to acoustic (sound) or from acoustic to electric. Examples include a microphone, earphones and loudspeakers.
- electroluminescence
Conversion of electrical energy into light energy.
- electrolyte
Electrically conducting liquid (wet) or paste (dry)
- electrolytic capacitor
A capacitor having an electrolyte between the two plates. A thin layer of oxide is deposited on only the positive plate. The oxide acts as the dielectric for the capacitor. Electrolytic capacitors are polarized and so must be connected in correct polarity to prevent breakdown.
- electromagnet
A coil of wire usually wound on a soft iron or steel core. When current is passed through the coil a magnetic field is generated. The core provides an easy path for the magnetic lines of force. This concentrates the field in the core.
- electromagnetic communication
Use of an electromagnetic wave to pass information between two points. Also called wireless communication. - electromagnetic induction
Voltage produced in a coil due to relative motion between the coil and magnetic lines of force.
- electromagnetic spectrum
List or diagram showing the range of electromagnetic radiation.
- electromagnetic wave
Wave taht consists of both electric and magnetic variation.
- electromagnetism
Relates to the magnetic field generated around a conductor when current is passed through it.
- electromechanical transducer
Device that transforms electrical energy into mechanical energy (electric motor) or mechanical energy into electrical energy (generator).
- electromotive force
(emf) Force that causes the motion of electrons due to potential difference between two points. (voltage)
- electron
Smallest sub atomic particle of negative charge that orbits the nucleus of an atom.
- electron flow
Electrical current produced by the movement of free electrons towards a positive terminal.
- electrostatic
Related to static electric charge.
- electrostatic field
Force field produced by static electrical charges.
- emitter
The semiconductor region from which charge carriers are injected into the base of a bipolar junction transistor.
- emitter feedback
Coupling from the emitter output to the base input of a bipolar junction transistor.
- emitter follower
A common collector amplifier. Has a high current gain, high input impedance and low output impedance.
- energized
Being electrically connected to a voltage source so the device is activated.
- energy
Capacity to do work.
- engineering notation
A floating point system in which numbers are expressed as products consisting of a number greater than one multiplied by an appropriate power of ten that is some multiple of three.
- enhancement-mode MOSFET
A field effect transistor in which there are no charge carriers in the channel when the gate source voltage is zero. - equivalent resistance
Total resistance of all the individual resistances in a circuit.
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I
- IC
Abbreviation for "integrated circuit"
- IC voltage regulator
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 occuring 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 occuring 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 outptu.
- 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.
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Q
- Q
Quality factor of an inductor or capacitor. It is the ratio of a component's reactance (energy stored) to its effective series resistance (energy dissipated). For a tuned circuit, a figure of merrit used in bandwidth calculations. Q is the ratio of reactive power to resistive power in a tuned circuit. Also the symbol for charge in coulombs (Q for quantity).
- quiescent
At rest. For an amplifier the term is used to describe a condition with no active input signal.
- quiescent point
(Q point) A point on the DC load line of a given amplifier that represents the quiescent (no signal) value of output voltage and current for the circuit.
R
- radar
Acronym for "radio detection and ranging" A system that measures the distance and direction of objects.
- radioastronomy
Branch of astronomy that studies the radio waves generated by celestial bodies and uses these emissions to obtain information about them.
- radio broadcast
Transmission of music, voice and other information on radio carrier waves that can be received by the general public.
- radiocommunication
Term used to describe the transfer of information between two or more points by use of radio or electromagnetic waves.
- radio-frequency amplifier
Amplifier having one or more active devices to amplify radio signals.
- radio-frequency generator
Generator capable of supplying RF energy at any desired frequency in the radio-frequency spectrum.
- radio-frequency probe
Probe used in conjunction with an AC meter to measure radio-frequency signals.
- RC
Abbreviation for "resistance capacitance" also abbreviation for "radio controled" as in "RC model airplanes."
- RC time constant
Product of resistance and capacitance in seconds.
- reactance
Symbol "X". Opposition to current flow without the dissipation of energy. Example: The opposition provided by inductance or capacitance to AC current.
- reactive power
Also called imaginary power or wattless power. It is the power value in "volt amps" obtained from the product of source voltage and source current in a reactive circuit.
- real number
Number having no imaginary part.
- receiver
Unit or piece of equipment used to receive information.
- recombination
Process by which a conduction band electron gives up energy (in the form of heat or light) and falls into a valence band hole.
- rectangular coordinates
A Cartesian coordinate of a Cartesion coordinate system whose straight-line axes or coordinate planes are perpendicular.
- rectangular wave
Also known as a pulse wave. A repeating wave that only operates between two levels or values and remains at one of these values for a small amount of time relative to the other value.
- rectification
Process that converts alternating current to direct current. - rectifier
Diode circuit that converts alternating current into pulsating direct current.
- reed relay
Relay consisting of two thin magnetic strips within a glass envelope. When a coil around the envelope is energised, the relay,s contacts snap together making a connection between leads attached to the reed strips.
- regenerative feedback
Positive feedback. Feedback from the output of an amplifier to the input such that the feedback signal is in phase with the input signal. Used to produce oscillation.
- regulated power supply
Power supply that maintains a constant output voltage under changing load conditions.
- regulator
Device or circuit that maintains a desired output under changing conditions.
- relay
Electromechanical device that opens or closes contacts when a current is passed through a coil.
- relative
Not independent. Compared with or with respect to some other measured quantity.
- relaxation oscillator
Free running circuit that outputs pulses with a period dependent or one or more RC time constants.
- reluctance
Resistance to the flow of magnetic lines of force.
- remanence
Amount a material remains magnetized after the magnetizing force has been removed.
- residual magnetism
Magnetism remaining in the core of an electromagnet after the coil current is removed.
- resistance
Symbolized "R" and measured in ohms. Opposition to current flow and dissipation of energy in the form of heat.
- resistive power
Amount of power dissipated as heat in a circuit containing resistive and reactive components. True power as opposed to reactive power.
- resistive temperature detector
(RTD) Temperature detector consisting of a fine coil of conducting wire (such as platinum) that will produce a relatively linear increase in resistance as temperature increases.
- resistivity
Measure of a material's resistance to current flow.
- resistor
Component made of material that opposes flow of current and therefore has some value of resistance.
- resistor color code
Coding system of colored stripes on a resistor to indicate the resistor's value and tolerance.
- resonance
Circuit condition that occurs at the frequency where inductive reactance (XL) equals capacitive reactance (XC).
- reverse bias
Bias on a PN junction that allows only leakage current (minority carriers) to flow. Positive polarity on the n-type material and negative polarity to the p-type material.
- reverse breakdown voltage
Amount of reverse bias that will cause a PN junction to break down and conduct in the reverse direction.
- reverse current
Current through a diode when reverse biased. An extremely small current also referred to as leakage.
- reverse saturation current
Reverse current through a diode caused by thermal activity. This current is not affected by the amount of reverse bias on the component, but does vary with temperature.
- RF
Abbreviation for "radio frequency."
- rheostat
Two terminal variable resistor used to control current.
- right angle triangle
Triangle having a 90° or square corner.
- ripple frequency
Frequency of the ripple present in the output of a DC source.
- ripple voltage
The small variations in Dc voltage that remain after filtering in a power supply.
- rise time
Time for the leading edge of a pulse to rise from 10% of its peak value to 90% of its peak value.
- RL differentiator
An RL circuit whose output voltage is proportional to the rate of change of the input voltage.
- RL filter
Selective circuit of resistors and inductors that offers little or no opposition to certain frequencies while blocking or attenuating other frequencies.
- RL integrator
RL circuit with an output proportionate to the integral of the input signal.
- rms
Abbreviation for "root mean square"
- rms value
Rms value of an AC sine wave is 0.707 times the peak value. This is the effective value of an AC sine wave. The rms value of a sine wave is the value of a DC voltage that would produce the same amount of heat in a heating element.
- roll-off rate
Rate of change in gain when an amplifier is operated outside of its bandwidth.
- rotary switch
Electromechanical device that has a rotating shaft connected to one terminal capable of making or breaking a connection to one or more other terminals.
- R-2R ladder
Network or circuit composed of a sequence of L networks connected in tandem. Circuit used in digital to analog converters.
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S
- 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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- watt
- Unit of electrical power required to do work at the rate of one joule per second. One watt of power is expended when one ampere of direct current flows through a resistance of one ohm. In an AC circuit, true power is the product of effective volts and effective amperes, multiplied by the power factor.
- wattage rating
- Maximum power a device can safely handle continously.
- watt-hour
- Unit of electrical work, equal to a power of one watt being absorbed for one hour.
- wattmeter
Instrument used to measure electric power in watts.
- wave
Electric, electromagnetic, acoustic, mechanical or other form whose physical activity rises and falls or advances and retreats periodically as it travels through some medium.
- waveform
Shape of a wave.
- waveguide
Rectangular or circular pipe used to guide electromagnetic waves at microfrequencies.
- wavelength
(l) Distance between two points of corresponding phase and is equal to waveform velocity divided by frequency.
- weber
(Wb) Unit of magnetic flux. One weber is the amount of flux that when linked with a single turn of wire for an interval of one second will induce an electromotive force of one volt.
- wien-bridge oscillator
Oscillator that uses an RC low-pass filter and an RC high-pass filter to set the frequncy of oscillations.
- wet cell
Secondary cell using a liquid as an electrolyte.
- wetting
Term used in soldering to describe the condition that occurs when the metals being soldered are hot enough to melt the solder so it flowes over the surface.
- wheatstone bridge
Four arm bridge circuit used to measure resistance, inductance or capacitance.
- wideband amplifier
Also called "broadband amplifier." Amplifier with a flat response over a wide range of frequencies.
- winding
One or more turns of a conductor wound in the form of a coil.
- wire
Single solid or stranded group of conductors having a low resistance to current flow. Used to make connections between circuits or points in a circuit.
- wire gauge
American wire gauge (AWG) is a system of numerical designations of wire diameters.
- wireless
Term describing radio communication that requires no wired between two communicating points.
- wirewound resistor
Resistor in which the resistive element is a length of high resistance wire or ribbon usually nichrome wound onto an insulating form.
- wire wrapping
Method of making a connection by wrapping wire around a rectangular pin.
- woofer
Large loudspeaker designed primarily to reproduce low frequency audio signals.
- work
Work is done any time energy is transformed from one type to another. The amount of work done is dependent on the amount of energy transformed.
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Last updated: Monday, March 3, 2008, 03:26 PM
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