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Power Supplies A to Z : "A"

We've included this handy glossary to help with the terminology & abbreviations relating to power products. Pick a letter below to begin, or download the glossary to refer to it whenever you like.

A B C D E F G H I J K L M N O P Q R S T U V W X-Z #


Abbreviation for ampere


Abbreviation for Alternating Current (Written in lower case 'ac')

ac Brownout

See Brownout.

ac Line

A conductor that routes ac voltage from one point to another.

ac Line Filter

A circuit placed in the ac line to remove unwanted noise from the ac supply.

ac Loss Detector

A power fail detector circuit that monitors the status of the ac lines.


The correctness of the indicated value.

Accuracy Limits

See Total Regulation.

ac-dc converter

A device that changes ac input voltage/current to a different dc output voltage/current. See also Power Supply.

Adjustment Range

The range over which the parameter (usually applies to output voltage or output current of a power supply) may be adjusted. See also Setting Range.

Air Gap

The separation between magnetic materials used to lower the permeability and increase the ampere turns before the materials saturate.

Alternating Current (ac)

Current which changes the direction in which it flows.

Alternating Current

Ambient Temperature

The average temperature of the environment immediately surrounding the power supply (PSU). For forced air-cooled units, the ambient temperature is measured at the air intake. See also Operating Temperature Range, Storage Temperature, Temperature Coefficient.

American National Standards Institute (ANSI)

United States standards agency located in New York.

American Wire Gauge (AWG)

A standard for sizing the diameters of wire and for measuring sheet-metal thicknesses.

Ampere (A)

The unit of current. 1 Ampere is equal to a flow of one coulomb of charge per second. SI definition is the current which, if maintained in two straight parallel conductors of infinite length, of negligible circular cross-section, and placed 1 metre apart in a vacuum, would produce a force equal to 2 x 10-7 newtons per metre of length. Written as 'ampere' or 'amp'. By Ohm's Law, a current of 1 amp through a resistance of 1 ohm will cause a potential difference of 1 volt.


Abbreviation for American National Standards Institute.

Apparent Power

Conventionally expressed in VA (volt-amperes). Apparent Power = currentrms x voltagerms.


Abbreviation for Automatic Test Equipment.


SI prefix multiplier. Multiplies by 10-18. So 100 aF = 100 x 10-18 F. Written as 'atto'. Abbreviated to 'a'.

Automatic Test Equipment (ATE)

Is any automated device that is used to test any other related electronic components or modules. It is usually a combination of hardware and software.

Auto-Range Input

The ability for a power supply to automatically operate from a different input voltage ranges. A typical specification for auto range input would be 100Vac to 132Vac and 180Vac to 253Vac. Compare with Wide Range Input.


A single winding transformer with one or more taps.

Auxiliary Supply

A power source supplying power other than the main load power. This is often an additional output on a power supply for system housekeeping which gives low current and is usually not inhibited with the main output.

Averaging Filter

See L-C Filter.


Abbreviation for American Wire Gauge.

A B C D E F G H I J K L M N O P Q R S T U V W X-Z #

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