PROBLEM TO BE SOLVED: To provide an LC oscillation circuit formed into LSI or a voltage-controlled LC oscillation circuit formed into LSI which has a small phase noise and can perform a low power supply voltage operation and oscillation of a high-frequency signal.;SOLUTION: In the LC oscillation circuit or the voltage-controlled LC oscillation circuit, a circuit in which a primary side inductor element (primary coil) and a fixed capacitance element or a variable capacitance element of a transformer are connected in parallel is connected as a load to an output terminal of a transistor element, and a signal of the output terminal is reversed and a signal voltage is fed back to an input terminal of the transistor element. In this circuit, in order to generate a current waveform having the same phase as that of a voltage waveform of the output terminal of the transistor element, a variable gain amplifier circuit employing a second transistor element in which a current applied to an output terminal increases as a voltage of the input terminal increases or a plurality of transistor elements is prepared, and an in-phase current is applied to a secondary side inductor element (secondary coil) coupled to the primary side inductor element (primary coil) of the transformer.;COPYRIGHT: (C)2008,JPO&INPIT
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