Electronic Engineering Dictionary

AT-Cut Crystal. A particular crystal cut at 35 degrees to the Z axis.

Attachment Unit Interface. [AUI] In a local area network, the interface between the medium access unit (MAU) and the data terminal equipment within a data station.

Attenuate. To reduce in amplitude.

Attenuation. The decrease in magnitude of a signal as it travels through any transmitting medium, such as a cable or circuitry. The ability of a filter circuit to reduce the amplitude of unwanted frequencies to a level below that of the desired output frequency. More detail on 24AWG twisted pair copper wire attenuation
[Resistor Chip Attenuator Manufacturers, RF Attenuator Manufacturers]. The attenuation of an attenuator is the ratio of power into a component to the power out under matched conditions, and represents the actual power dissipated within the attenuator.

L-Pad Attenuator Circuit

Attenuation Coefficient. The rate of diminution of average power with respect to distance along a transmission path.

Attenuation Constant. The real part of the propagation constant in any electromagnetic propagation medium.

Attenuation Distortion. The difference in loss at specified frequencies relative to the loss at 1004 Hz, unless otherwise specified.

Attenuation Network. A group of [impedance] components arranged to attenuate a signal.

Attenuator. A resistive component inserted into a circuit to reduce signal amplitude. A network that reduces the amplitude of a signal without appreciably distorting its waveform.

Attenuator Pad. A component inserted into a transmission path to introduce transmission loss.

Attraction. The force that tends to make two objects approach each other. Attraction exists between two unlike magnetic poles (north and south) or between two unlike static charges.

Audio. Sound between the range of 15 hertz (15 Hz) and 20 kilohertz (20 kHz).

Audio Amplifier. An amplifier designed to amplify frequencies between 15 hertz (15 Hz) and 20 kilohertz (20 kHz), which relates to the frequency range of human hearing. Voice bandwidth on a phone line is limited to between 300Hz and 3.4KHz. The transistor Q1 is the amplifier in the circuit to the right [Example Audio Amplifier Circuit].

Audio Frequency. [AF] The band of frequencies (approximately 20 Hz to 20 kHz) that, when transmitted as acoustic waves, can be heard by the normal human ear.

Audio-Frequency-Tone Shift. A system that uses amplitude modulation to change dc mark and space impulses into audio impulses.

Autodyne. A circuit that combines the functions of an RF amplifier, mixer and local oscillator.

Automatic Bias. The DC bias developed on the Base circuit as a result of current flowing in the Collector circuit due to a resistor placed in the Emitter circuit [of a transistor]. A FET would use the gate, Source, Drain nomenclature.

Automatic Frequency Control. [AFC] A device or circuit that maintains the frequency of an oscillator within the specified limits with respect to a reference frequency. A circuit that produces an error signal in proportion to the amount of frequency drift from a reference frequency.

Automatic Gain Control. [AGC] A circuit used to limit variations in the output signal strength of a receiver. A process or means by which gain is automatically adjusted in a specified manner as a function of a specified parameter, such as received signal level.

Auto Ranging. A method of automatically changing the characteristics of a circuit to accommodate changes in the input which would other wise not be within the operational range of the amplifier.

Auto-Transformer. A transformer with only one winding. The secondary side [same winding] has two or more fixed taps or a movable tap and a common point with the primary. Also refer to Transformer Terms

Auxiliary Power. Electric power that is provided by an alternate source and that serves as backup for the primary power source at the station main bus or prescribed sub-bus.

Avalanche Breakdown. A type of breakdown that occurs in semiconductors. A sudden change from high dynamic electrical resistance to very low dynamic resistance in a reverse biased semiconductor device.

Avalanche Effect. A reverse breakdown effect in diodes that occurs at reverse voltages beyond 5 volts. The released electrons are accelerated by the electric field, which results in a release of more electrons in a chain or "avalanche" effect. Related terms, from Zener Diode Definitions.

Avalanche Photodiode. [APD] A photodiode that is intended to take advantage of avalanche multiplication of photocurrent. A photodiode that operates with a reverse-bias voltage that causes the primary photocurrent to undergo amplification by cumulative multiplication of charge carriers.

Average Power. The peak power value averaged over the pulse-repetition time. Output power of a transmitter as measured from the start of one pulse to the start of the next pulse.

Average Seek Time. For Hard Disk Drives [HDD] the average seek time is the amount of time it takes for a head to seek out the specified address, which is calculated over a large number of random seeks.

Average Value (of AC). The average of all the instantaneous values of one-half cycle of alternating current.

Avionics. Electronic systems related to aircraft equipment [AVIation electrONICS] . Different types of Avionics Data Buses.

Axial Impeller Fan. An item with blades or vanes equally spaced radially around the periphery of a hub, flange, or rotor. It is the rotating part of an axial type fan, electric motor, or generator, which creates a flow of air or gas parallel to the axis of rotation.

Axial Lead. An electrical component that has its terminals [leads] protruding out two sides of the component body, along the devices axis. A through-hole component. Refer to a picture of an axial leaded component to the right.

Axis. A straight line passing through an object to denote its center.

Azimuth. Angular measurement in the horizontal plane in a clockwise direction.