Oscillator circuit and L load differential circuit achieving a wide oscillation frequency range and low phase noise characteristics
View Patent ↗An oscillator circuit is formed of a differential LC resonant circuit formed of an L load differential circuit including inductance-variable portions and a capacitor element, and a positive feedback circuit formed of N-channel MOS transistors. The inductance-variable portion is configured to vary the inductance by selecting a plurality of switch circuits arranged between a plurality of arbitrary positions on a spiral interconnection layer and the input/output terminal, and thereby can control an oscillation frequency. The inductance-variable portions form an inductor pair when the switch circuit among the switch circuits coupled between the first input/output terminals is turned on together with the switch circuit.
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 plurality of spiral interconnection layers starting from said first input/output terminal, and
a plurality of second switch circuits coupled between trailing ends of said plurality of interconnection layers and said second input/output terminal, respectively,
when one of said plurality of second switch circuits is turned on, the trailing end of said interconnection layer included in said plurality of interconnection layers and 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.