Voltage-controlled oscillator generating output signal finely tunable in wide frequency range and variable delay circuits included therein

Abstract

A voltage-controlled oscillator includes a plurality of variable delay circuits, wherein a first differential output signal of an adjacent previous stage is provided as a first differential input signal and a second differential output signal of a second previous stage is provided as a second differential input signal. Each variable delay circuit includes a loading circuit including first and second loading units, a first input circuit including first and second input transistors gated by the first differential input signal, a second input circuit including third and fourth input transistors gated by the second differential input signal, first and second current sources connected between a first common node and a second power source and in electrical parallel with each other, and third and fourth current sources connected between a second common node and the second power source and in electrical parallel with each other.