Oscillator

From OpenCircuits
Revision as of 21:41, 16 January 2008 by 64.61.84.2 (talk)
Jump to navigation Jump to search

ichat plastic sheeting birthday cards free greetings little miami school ohio missouri counties and zip codes noticias univision orlando safeway insurance of georgia pacific palm cima katarina witt nackt drug forum passing test spacecraft systems engineering adults funny stuff embroidered baby blankets where to buy viagra on line writing instruction manual a bugs life hedge trimmers cingularwireless.com my account making fake pussy sphere of influence map cagiva e900 decorative victorian bird house latina women songwriting duos ovarian cancer stage iii martin clunes actor 91410 orwell high school felixstowe play games commercial christmas decorations buying gas room divider wholesale retro handbags wholesale air cleaner filter kuwait offset program sacajawea www.scotiabank.com pinnacle airline poker star strip resepi lauk pauk free ebony big booty movie real estate malvern pa texas road house statutory legislation texas dwi law lawyer off broadway shows adultvideo girl most teenage thong wear im afraid of americans music video download women pics 3 landscape point rake sms program mn purchase agreement abc bracket ncaa milos naked sofia budget web host dirty daisy savannah convention and visitor bureau world of warcraft priest hip hop news purchase computers online boot short ugg ultra old ford truck parts video software bad credit special finance car loan trillian messenger race and sentencing lstat example property consultants denia dragula lyric cherry patch ranch little richer africa art fine photograph leather backpack purse peace of my heart lyrics sitting waiting wishing tablature girl sex teen outcomes research conferences natural hormone replacement aria movie clips syria news.com entertainment news yahoo scoring machine down payment assistance bradley airport hartford ct maryland welding rod lawyer install software windows xp fire and ice used off road go karts for sale overseas online pharmacy naturism 3d screensavers mark tremonti cystic fibrosis cpap mask lychee daquiri recipe auschwitz survivor story overcoming obstacles quotations jean keating work shop sophie falkiner inspirational religious poem organic items ea international academy of design technology nashville tennessee refurb macintosh anti semitism definition justin live timberlake first time home buyer body builder female free porn policy on linkage katie holmes pics netherlands flower lactating breasts milky breast microsoft office 2004 torrent dogs having sex with men long soft dick sociologico lord alfred douglas poetry free adaware spyware parental control gazpacho technically savvy airfrance york county sc courthouse disney channel.com diesel engine man marine playland auction book comic online fuck wife while husband watch flowmaster exhaust catholic bible premiership football result trion air bear replacement filter preparing presentation boat rentals havasu hack runescape character karens kreations patricia hewitt contact details power rangers spd episode summary krishna cottage rocky top farms veal sandwich adventure quest rpg cheat female genital piercings galleries kelly worth herb albert northwest airline baggage restriction no oh oh i wont stand in your way anymore firex carbon monoxide alarm The vast majority of electronic systems operate at some fixed frequency. Usually the component that fixes that frequency is a quartz crystal, sealed in a metal can. (Some very-low-cost devices might use a "ceramic resonator" (made of high-stability piezoelectric ceramics, generally lead zirconium titanate)or a resistor and a capacitor to fix the frequency. ).

The entire circuit that generates the frequency is called an "oscillator", includes the resonant part (crystal, resonator, or RC), some capacitors, and a silicon chip and therefore is called a hybrid device. (An oscillator that uses a resistor and a capacitor to fix the frequency is called a "RC oscillator". An oscillator that uses a crystal to fix the frequency is called a "crystal oscillator".)

The oscillator includes, in addition to the frequency-fixing component just mentioned, an amplifier and capacitors.

Oscillators usually come in a metal can, but Epson also encapsulates them in plastic. Typically an oscillator can has 4 pins. Inside the can is all the components of the oscillator. One applies DC power on 2 of the pins, and the oscillating signal (the "CLK OUT") appears on another pin. (The remaining pin is unused).

An oscillator can also be made from scratch using crystal in a (2-pin) metal can, a couple of capacitors, an resitor and an inverter. In either case, the frequency is printed on the top of the crystal or oscillator.

Many microcontrollers have 2 pins (typically labeled "XTAL1" and "XTAL2", or "OSC1" and "OSC2", or something similar) that are designed to be directly connected to the 2 pins of a crystal. (Capacitors from those pins to VCC and GND are also part of the recommended circuit). An inverter inside the microcontroller acts as the amplifier, and the crystal and capacitors make up the rest of the oscillator. Microcontrollers when connected directly to a crystal need to have capacitors attached that need to be percisely matched with other circuit components on the board. Resonators tend to have the capacitor buildin reducing the amount of trial and error of capacitor selection.

In systems with multiple CPUs, it is often simpler, cheaper, and more reliable (avoiding metastability problems) to use a single crystal (rather than a dedicated crystal for each CPU). CPUs (and many other components) often have a single "CLK" pin designed to be connected to the wire used to send that "clock signal" (a fixed frequency) everywhere.

Unfortunately, many people confuse the "clock signal" generated by an oscillator (a simple metronome beat, tone, at constant frequency) with far more complicated "clock system"s that keep track of seconds, minutes, hours, and sometimes days, weeks, months, and years.

for further reading