Patent ID: 6906596

Claim:
An LC resonant oscillation circuit comprising: an LC resonance circuit; a MOS transistor for supplying a bias current to said LC resonance circuit; a plurality of capacitive elements coupled to an output node of said LC resonance circuit, said plurality of capacitive elements being supplied with respective selection voltages at terminals thereof opposite to the output node for selecting an oscillating frequency band such that the oscillating frequency band is step by step changeable in accordance with said respective selection voltages; and a variable capacitive element coupled to the output node of said LC resonance circuit, the variable capacitive element being supplied with a variable voltage at a terminal opposite to the output node for tuning an oscillating frequency in the selected oscillating frequency band, said plurality of capacitive elements including at least one first capacitive element, the capacitance of which changes in accordance with a voltage applied thereto, said at least one first capacitive element including a terminal opposite to said output node, and the opposite terminal of said at least one first capacitive element being supplied with a voltage for measuring an amplitude of an output signal of the LC resonant oscillation circuit.