Phase locked loop.

摘要

An improved phase locked loop utilizing control logic generated by a phase detector to eliminate sensitivity to uncorrelated noise when the loop is in lock. The phase locked loop comprises a differential filter (117) having first and second input lines. A logic element (115) is responsive to the locked state of the phase locked loop for connecting said first and second input lines together whereby uncorrelated noise is common-mode to the filter and, as such, does not affect the VCO (121) input. The phase locked loop is particularly useful in clock signal synthesis and in an IC used to display video signals.