Patent ID: 7023287

Claim:
A voltage-controlled oscillator comprising: a voltage-controlled oscillation circuit that oscillates at a frequency according to a control voltage; and a limiter circuit that, if an output of the voltage-controlled oscillator is higher than a predetermined level, limits the output of the voltage-controlled oscillator to the predetermined level, wherein, even when, according to the control voltage, the output of the voltage-controlled oscillator varies along with the frequency at which the voltage-controlled oscillator is oscillating, if the output of the voltage-controlled oscillator is higher than the predetermined level, an output of the limiter circuit is kept at a constant level, wherein the limiter circuit includes a differential amplifier circuit that receives the output of the voltage-controlled oscillation circuit and operates in a saturated state, wherein the differential amplifier circuit operates from an operation current produced by a constant current source that produces a constant current by applying a predetermined voltage to a current producing resistor.