Phase detector

A phase detector or phase comparator is a circuit which compares the phase of an oscillation with a phase reference defined in the vibration and in case of a phase modulation, to output the phase difference as a signal. A phase detector is needed in the phase - locked loop circuit.

Phase comparator may be implemented analog or digital. Digital phase comparators are, for example, XOR gates. The output will be a pulse voltage, the duty cycle and thus the arithmetic average of the phase shift change with the two input voltages Ux and Us.

Phase detectors can also be implemented with flip-flops ( see schematic diagram). The advantage over the solution to the XOR gate is that you can due to the two outputs ( P and N ) can also tell whose edge first flip-flop has switched.