A
voltage controlled oscillator of the present invention includes power supply terminal (101), control terminal (2) for controlling an output frequency, output terminals (3a, 3b), cross-coupled transistors (5a, 5b), capacitances (6a, 6b, 7a, 7b), LC tanks (10a, 10b),
resistor (117), grounding
capacitance (18) and
center frequency control circuit (16).
Center frequency control circuit (16) includes resistors (11a, 11b), grounding
capacitance (12),
center frequency control terminal (4) for controlling a
center frequency of the output frequency, and
voltage-divider circuit (15). Resistors (11a, 11b) are connected to the base terminals of cross-coupled transistors (5a, 5b), the other ends of resistors (11a, 11b) are connected to each other, and, to this connecting point, one end of grounding
capacitance (12) and one end of
voltage-divider circuit (15) are connected. The other end of voltage-divider circuit (15) is connected to center frequency control terminal (4).