Editing Crystal oscillator (section)

{{Short description|Electronic oscillator circuit}}
{{Redirect|Pull capacitor|resistors|Pull-up resistor|and|Pull-down resistor}}
{{Redirect|Padding capacitor|adjustable capacitors|Trimmer capacitor}}
{{Use dmy dates|date=June 2022|cs1-dates=y}}
{{Infobox electronic component
|name              = Crystal resonator
|image             = 16MHZ Crystal.jpg
|image_size        = 200
|caption           = A miniature 16 [[MHz]] [[quartz crystal]] enclosed in a [[hermetically sealed]] HC-49/S package, used as the resonator in a crystal oscillator.
|type              = [[Electromechanical]]
|working_principle = [[Piezoelectricity]], [[Resonance]]
|invented          = [[Alexander M. Nicholson]], [[Walter Guyton Cady]]
|first_produced    = 1918
| symbol            = [[File:IEEE 315 Fundamental Items Symbols (113).svg|100px|class=skin-invert-image]]
| symbol_caption    = 
}}

A '''crystal oscillator''' is an [[electronic oscillator]] [[Electrical circuit|circuit]] that uses a [[piezoelectricity|piezoelectric]] [[crystal]] as a [[frequency selective surface|frequency-selective element]].<ref name="Graf1999">{{cite book 
  | last = Graf
  | first = Rudolf F.
  | title = Modern Dictionary of Electronics, 7th Ed.
  | publisher = Newnes
  | year = 1999
  | location = US
  | pages = 162, 163
  | url = https://books.google.com/books?id=o2I1JWPpdusC&q=graf+dictionary+%22crystal+oscillator&pg=PA163
  | isbn = 978-0750698665}}</ref><ref name="Amos">{{cite book   
  | last = Amos
  | first = S. W.
  |author2=Roger Amos
  | title = Newnes Dictionary of Electronics, 4th Ed.
  | publisher = Newnes
  | year = 2002
  | location = US
  | pages = 76
  | url = https://books.google.com/books?id=lROa-MpIrucC&q=dictionary+of+electronics+%22crystal+oscillator&pg=PA76
  | isbn = 978-0750656429}}</ref><ref name="Laplante">{{cite book   
  | last = Laplante
  | first = Phillip A. 
  | title = Comprehensive Dictionary of Electrical Engineering
  | publisher = Springer
  | year = 1999
  | location = US
  | url = https://books.google.com/books?id=soSsLATmZnkC&q=electronics+dictionary+%22crystal+oscillator&pg=PA152
  | isbn = 978-3540648352}}</ref> The oscillator frequency is often used to keep track of time, as in [[quartz clock|quartz wristwatches]], to provide a stable [[clock signal]] for [[digital data|digital]] [[integrated circuit]]s, and to stabilize frequencies for [[radio transmitter]]s and [[radio receiver|receiver]]s. The most common type of piezoelectric resonator used is a [[quartz]] crystal, so oscillator circuits incorporating them became known as crystal oscillators.<ref name="Graf1999" /> However, other piezoelectric materials including [[polycrystalline]] ceramics are used in similar circuits.

A crystal oscillator relies on the slight change in shape of a quartz crystal under an [[electric field]], a property known as inverse [[piezoelectricity]]. A voltage applied to the [[electrode]]s on the crystal causes it to change shape; when the voltage is removed, the crystal generates a small voltage as it elastically returns to its original shape. The quartz oscillates at a stable resonant frequency (relative to other low-priced oscillators) with frequency accuracy measured in [[parts per million]] (ppm). It behaves like an [[RLC circuit]], but with a much higher [[Q factor]] (lower energy loss on each cycle of oscillation and higher frequency selectivity) than can be reliably achieved with discrete [[capacitors]] (C) and [[inductors]] (L), which suffer from [[Parasitic element (electrical networks)|parasitic]] [[Resistance (electricity)|resistance]] (R). Once a quartz crystal is adjusted to a particular frequency (which is affected by the mass of electrodes attached to the crystal, the orientation of the crystal, temperature and other factors), it maintains that frequency with high stability.<ref>Paul Horowitz, Winfield Hill, ''The Art of Electronics Second Edition'', Cambridge University Press, 1989, {{ISBN|0-521-37095-7}},  pg. 300 ff</ref>

Quartz crystals are manufactured for frequencies from a few tens of [[kilohertz]] to hundreds of megahertz. As of 2003, around two billion crystals were manufactured annually.<ref>{{cite book |last=Lombardi|first=Michael |title=Encyclopedia of Physical Science and Technology |year=2003 |edition=3rd}}</ref> Most are used for consumer devices such as [[wristwatch]]es, [[clock]]s, [[radio]]s, [[computer]]s, and [[cellphone]]s. However, in applications where small size and weight is needed crystals can be replaced by [[thin-film bulk acoustic resonator]]s, specifically if ultra-high frequency (more than roughly 1.5&nbsp;GHz) resonance is needed. Quartz crystals are also found inside test and measurement equipment, such as counters, [[signal generator]]s, and [[oscilloscope]]s.