Loop filter and amplifier for improved phase margin and decreased phase noise with VCOs

A method of controlling a voltage controlled oscillator (VCO) in a phase-locked loop (PLL), comprising the steps of:

• receiving a variable analog offset voltage at a first input of an amplifier;
• providing a correction voltage to a second input of the amplifier;
• using the variable analog offset voltage to generate a first value of a control voltage;
• using the correction voltage to adjust the first value of the control voltage in order to generate a second value of the control voltage, wherein the variable analog offset voltage is summed with the correction voltage to increase the range of the control voltage;
• and
• providing the second value of the control voltage to the VCO, wherein the variable analog offset voltage is amplified more than the correction voltage.

A phase-locked loop (PLL), comprising:

• a voltage-controlled oscillator (VCO);
• a comparator coupled to an output of the VCO and configured to generate a correction voltage;
• and
• a loop filter and amplifier configured to generate a VCO control voltage by using the correction voltage to adjust an initial value of the VCO control voltage, wherein the amplifier sums the correction voltage and a variable analog offset voltage to generate the VCO control voltage, and wherein the amplifier amplifies the variable analog offset voltage more than the amplifier amplifies the correction-voltage.