Patent ID: 6593818
Filing Date: 2003-07-15
Classification: H03B,H03L

Abstract:
A PPL circuit having a reference signal comprising:a voltage controlled oscillator having first varicap diodes and to output a voltage signal; a loop filter connected to said voltage controlled oscillator; a compensation circuit to compensate leakage currents of said voltage controlled oscillator; a phase detector to generate a control voltage which is input to said loop filter, said control voltage being a function of a phase difference between a phase of said reference signal and a phase of said voltage signal; said compensation circuit having an operational amplifier connected in a voltage follower mode, second varicap diodes in the same configuration as said first varicap diodes, and a differential output; said compensation circuit connected to said voltage controlled oscillator by a control line, where one of said differential output outputs a signal that approximates said control signal and is connected to said first varicap diodes; and wherein said other output of said differential output outputs a current equal to the leakage from said second varicap diodes.