Voltage controlled oscillator

A voltage controlled oscillator controlling an oscillation frequency based on a control voltage supplied from an external control voltage terminal, the voltage controlled oscillator comprising:

• a reference bias voltage circuit generating a reference bias voltage by adjusting a reference voltage;
• and
• a gain adjustment circuit adjusting a gain of the control voltage,
• wherein the gain adjustment circuit includes (i) a plurality of resistances and (ii) a plurality of switching elements,
• wherein the gain adjustment circuit controls the plurality of switching elements and forms a voltage dividing circuit between the reference bias voltage and the external control voltage terminal to generate an automatic frequency control (AFC) voltage,
• wherein the gain adjustment circuit further includes a driving circuit driving each of the plurality of switching elements,
• wherein the reference bias voltage generating circuit includes (i) a plurality of serial resistances between the reference voltage and a ground and (ii) a switch coupled in parallel to at least one of the serial resistances, and
• wherein the reference bias voltage circuit controls the switch and changes a voltage dividing ratio of the serial resistances to set the reference bias voltage.

A voltage controlled oscillator controlling an oscillation frequency based on a control voltage supplied from an external control voltage terminal, the voltage controlled oscillator comprising:

• a reference bias voltage circuit generating a reference bias voltage by adjusting a reference voltage;
• and
• a gain adjustment circuit adjusting a gain of the control voltage,
• wherein the gain adjustment circuit includes (i) a plurality of resistances and (ii) a plurality of switching elements,
• wherein the gain adjustment circuit controls the plurality of switching elements and forms a voltage dividing circuit between the reference bias voltage and the external control voltage terminal to generate an automatic frequency control (AFC) voltage,
• wherein the control voltage is supplied through a serial resistance coupled to the external control voltage terminal,
• wherein the voltage dividing circuit couples the control voltage with the reference bias voltage circuit directly or through at least one of the resistances, based on a connecting state of the plurality of switching elements to change the AFC voltage,
• wherein the reference bias voltage circuit includes (i) a plurality of serial resistances between the reference voltage and a ground and (ii) a switch coupled to at least one of the serial resistances in parallel, and
• wherein the reference bias voltage circuit controls the switch and changes a voltage dividing ratio of the serial resistances to set the reference bias voltage.