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 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 that 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.

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 dielectric 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.

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 halfway 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 dielectric 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 wave