Circuit for compensating charge leakage in a low pass filter capacitor of PLL systems

摘要

The present invention provides for a phased locked loop. A capacitor has an associated leakage current. A differential circuit is coupled to the capacitor of a low pass filter. A voltage follower circuit is coupled to the output of the differential circuit. The gate of a field effect transistor (FET) is coupled to an output of the voltage follower circuit. A current mirror is coupled to the FET, the current mirror having a first source and a second source, wherein the second current mirror source is coupled to the drain of the FET, wherein an output of the first current mirror source is coupled to the capacitor. Through the employment of current mirror source, leakage charge within the capacitor is replaced.