A basic introduction to Phase Locked Loops

Posted on Tuesday, February 21st, 2012 in tutorials by DP

Kenneth was curious about Phase Locked Loops so he decided to dive into them. PLLs generate an output signal that is phase-synchronized to an input signal. They are widely used in telecommunication, radio, and computer systems. One place we commonly find PLLs is the frequency multiplier circuit inside microcontrollers.

The inevitable next step was to break out the breadboard, put together a simple PLL, and just play with it some to try and really get the concept.  Luckily, the classic 4000 logic series includes the 4046 PLL chip, which includes both a voltage controlled oscillator and both types of phase detectors.  After putting it all together, I figured I’d record a video and let you enjoy the play-by-play as I try and break it all down for you.

Check out the video below the fold.

This entry was posted on Tuesday, February 21st, 2012 at 9:00 pm and is filed under tutorials. You can follow any responses to this entry through the RSS 2.0 feed. You can skip to the end and leave a response. Pinging is currently not allowed.

5 Responses to “A basic introduction to Phase Locked Loops”

  1. JBeale says:

    The 4046 is a neat part. It doesn’t go much above 1 MHz though; if you want a similar part which can operate at higher frequencies, the NXP 74HCT9046A can go to 11 MHz (minimum).

  2. The 74HCT7046 also has a respectable top frequency on its VCO.

    I’m currently working on some follow-up using the HC4046 as a programmable frequency synthesizer, so watch for updates.

  3. Christian says:


  4. Lars says:

    Really nice and informative presentation, thanks.

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