Patent ID: 7202754
Filing Date: 2007-04-10
Classification: H03B

Abstract:
1. An oscillator circuit, comprising: a pair of transistors cross-coupled to each other; and an LC resonant circuit of a differential type coupled to said pair of transistors in a feedback manner; wherein said LC resonant circuit includes first and second inductance-variable portions including first and second input/output terminals, said second input/output terminals being commonly connected to a fixed node, and said first and second inductance-variable portions being capable of varying inductances, and a first switch circuit coupled between the first input/output terminals of said first and second inductance-variable portions, each of said first and second inductance-variable portions has a spiral interconnection layer starting from said first input/output terminal, and a plurality of second switch circuits having first terminals connected to arbitrary positions on said interconnection layer, respectively, and having second terminals commonly connected to said second input/output terminal, when one of said plurality of second switch circuits is turned on, the position on said interconnection layer connected to said turned-on second switch circuit is electrically coupled to said second input/output terminal, and when said first switch circuit is turned on in response to the turn-on of said second switch circuit, said first switch circuit electrically couples said first and second inductance-variable portions.