Voltage-controlled oscillator and phase-locked loop

A phase-locked loop, comprising:

• a phase-frequency detector, configured to detect a difference between a reference clock and a feedback clock to output a detection signal;
• a charge pump, configured to generate a charging/discharging signal according to the detection signal;
• a first filtering circuit, configured to determine an input voltage according to the charging/discharging signal;
• a voltage-controlled oscillator, comprising:
• an input circuit, comprising:
• an operational amplifier, configured to generate an output voltage according to the input voltage and a feedback voltage;
• a first input transistor, configured to generate an input current according to the output voltage and a power supply voltage;
• a second input transistor, comprising:
• a high voltage terminal, coupled to a low voltage terminal of the first input transistor and a non-inverting terminal of the operational amplifier;
• a control terminal, coupled to the high voltage terminal of the second input transistor;
• and
• a low voltage terminal, coupled to a low potential terminal;
• and
• a third input transistor, configured to generate a mirror current according to the input current;
• a first current supply circuit, configured to generate a first output current according to the input current;
• a second current supply circuit, configured to generate a second output current according to the input current;
• a second filtering circuit, coupled to the input circuit and the second current supply circuit, and configured to reduce an influence caused by a variation of the input current on the second current supply circuit;
• and
• an oscillating circuit, configured to generate an output clock according to the first output current and the second output current;
• and
• a loop divider, configured to generate the feedback clock according to the output clock,
• wherein a ratio of a filter bandwidth of the second filtering circuit to a loop bandwidth of the phase-locked loop is not larger than 0.01.