Voltage-controlled oscillator including first and second varactors having differing rates of change in capacitance value

摘要

A Colpitts voltage-controlled oscillator is provided with a variable capacitance section 11 connected in parallel to a resonator 12, which is the inductance element of an inductance section 1. Variable capacitance section 11 is provided with varactors X1 and X2 having differing voltage/capacitance ratios. A fixed control voltage Vc is applied to the commonly connected cathodes of varactors X1 and X2. A control voltage Va which produces a reverse bias voltage (Vc-Va) is applied to the anode of varactor X1, and a control voltage Vb which produces a reverse bias voltage (Vc-Vb) independent of control voltage Va is applied to the anode of varactor X2. When control voltage Va is fixed, control voltage Vb is made the frequency control signal, and when control voltage Vb is fixed, control voltage Va is made the frequency control signal.