Electronics notes/Phase Locked Loop notes: Difference between revisions

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From a functional, 'why would you do this' level, a phase locked loop means making one oscillator (or oscillating-style signal) follows another so that it will match the measured phase.
From a functional, 'why would you do this' level, a phase locked loop means making one oscillating thing follow another.




The frequency of both should probably be close to start with for that to lock in well - which also means (measured) frequency will match.


...and if it's significantly different, it becomes a multiplier, or strangely modulating thing - I've seen the latter used for interesting suboscillator-style behaviour in synths.  
For an analogy, two oldschool car blinkers.


These drift quickly {{comment|(While bimetal blinkers are roughly the clunkiest way to do this, but even if you manufacture them extremely well they would still drift)}}


Applications include, creating copies of clocks, having those be cleaner than the original, creating multiples of clocks multiplication.
Say you have two imprecise bimetal blinkers, and you could forcibly make one start ''when'' the other one triggers, then they would keep the same speed.
 
 
 
 
For an analogy, two oldschool car blinkers, would always go out of phase. Bimetal flashers are roughly the clunkiest way to do this, but even if you manufacture them well they would still go out of phase.
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Electronic circuits are more precise - but still have too many parts that vary in production specs and/or vary with temperature.
They too will still drift. But because things like cheap watch crystals have been a thing for decades, you can make that drift slow for very cheap.
 
[https://www.youtube.com/watch?v=2z5A-COlDPk]-->
 
Say you have two imprecise bimetal blinkers, and you could forcibly make one trigger ''when'' the other one triggers, then even these messy components would never perceptibly drift.




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PLL is a little more than that.
PLL is a little more than that.


PLL says "okay, you've got an oscillator, and you've got a reference signal you want to synchronize to.
There are a few variant implementations,  
but they are generally described as


We'll build a feedback system that will tune our own oscillator to match the reference, in phase and frequency"
"we have an oscillator, and you're feeding us a reference signal you want to synchronize to.
  we'll build a feedback system that will tune our own oscillator to match the reference, in phase and frequency"




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: which is not very hard when it is a VCO -- because that means 'voltage controlled'
: which is not very hard when it is a VCO -- because that means 'voltage controlled'


The phase difference detector only really gives sensible "slight corrections to keep it in phase" output when the VCO is already at more or less the right frequency.




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* frequency synthesizers, which govern communication between chips {{verify}}
* frequency synthesizers, which govern communication between chips {{verify}}
* creating copies of clocks,
:: and having that be cleaner than the original
* creating multiples a clock signal.
* altered version to becomes a frequency multiplier
* if you feed it audio, you will get some fuzz-like imitation
The first few meaning they are common in communication and computers.




Revision as of 01:29, 26 August 2023

⚠ This is for beginners and very much by a beginner / hobbyist

It's intended to get an intuitive overview for hobbyist needs. It may get you started, but to be able to do anything remotely clever, follow a proper course or read a good book.

Some basics and reference: Volts, amps, energy, power · batteries · resistors · transistors · fuses · diodes · capacitors · inductors and transformers · ground

Slightly less basic: amplifier notes · varistors · changing voltage · baluns · frequency generation · Transmission lines · skin effect

And some more applied stuff:

IO: Input and output pins · wired local IO · wired local-ish IO · ·  Various wireless · 802.11 (WiFi) · cell phone

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Audio notes: See avnotes


Platform specific

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Less sorted: Ground · device voltage and impedance (+ audio-specific) · electricity and humans · power supply considerations · Common terms, useful basics, soldering · landline phones · pulse modulation · signal reflection · Project boxes · resource metering · SDR · PLL · vacuum tubes · Multimeter notes Unsorted stuff

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See also Category:Electronics.

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