Glossary - alphabet order - "A"

AT crystal unit, AT cut crystal unit

This is a crystal unit that has a crystal chip that was cut at the "AT cut" angle from the quartz crystal crystallographic axis. This is one of the most widely used types of crystal units, which covers the Megahertz (MHz) band. Since this type of unit has frequency - temperature characteristics for cubic functions with inflection point near room temperature, it has excellent temperature characteristics.

Reference: frequency versus temperature characteristics

Absolute maximum rating

Absolute maximum ratings provide for items and ranges of values to prevent damage of the crystal device or critical changes in characteristics.

APR (Absolute Pull Range)

The range of frequencies that can be controlled from the nominal frequency value. In other words, APR = Frequency Control Range - Frequency Deviation (Frequency Tolerance).

Accumulated jitter

A type of jitter defined in specification. See "jitter".

Reference: Jitter

Allowance of oscillation

This allowance is expressed as a ratio between a crystal oscillation circuit's negative resistance and a crystal unit's CI value. It is a parameter that indicates the quality of the oscillation characteristics.

Anti-reflection coating

It is a thin film deposited on the surface of an optical component by evaporation to reduce surface reflections. One typical example is a single-layer made of magnesium fluoride (MgF2.) and there are also multi-layered films that further reduce reflectivity.
4 to 8 % of incident light is reflected on a glass.

Page Top