Detect Phase Differences in Input Signals
A phase detector outputs a PWM signal that represents the phase difference between the input signals. This video quickly explains how an XOR gate works as a phase detector.
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Hello, and welcome to The Logic Minute. In this video, we will look at how to determine the difference in phase between two clock signals with logic. A digital phase detector compares two 50% duty cycle clock signals operating at the same frequency and generates an output that indicates the phase difference between them. A common application of this phase detector can be found in digital phase-locked loops. An XOR gate provides a small, simple, and low-power solution.
The truth table of the XOR gate is shown to the right. When the inputs are out-of-phase, they will be in opposite states, and the output of the XOR gate will go high. This behavior creates a PWM signal that represents the phase difference between the inputs. A 0% duty cycle at the output indicates that the inputs are in-phase, while 100% duty cycle indicates that the inputs are 180 degrees out-of-phase. It should be noted that this type of phase detector only gives the difference in phase and doesn't imply which input is leading or lagging.
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This video is part of a series
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Common applications of logic
video-playlist (20 videos) -
Common applications of gates
video-playlist (5 videos)