Patent ID: 7675376

Claim:
A voltage-controlled oscillator comprising: a first reactance circuit connected to a first terminal of an active element for oscillation; a second reactance circuit connected to a second terminal of said active element for oscillation; a third reactance circuit connected to a third terminal of said active element for oscillation; a load resistance connected to said third reactance circuit for outputting oscillation power amplified by said active element for oscillation; a variable-capacitance element which is provided to at least one of said first to third reactance circuits and varies its capacitance in response to a control voltage, said variable-capacitance element being composed of a plurality of varactor diodes which are connected in series; and a negative capacitance circuit whose slope of impedance with respect to frequency is opposite to that of a normal capacitance, and which is connected to at least one variable-capacitance element of said one or a plurality of variable-capacitance elements.