Circuits and methods for generating an oscillator output. The circuit generally includes a ring oscillator, with a series of inverters connected in series and an LC resonator tank (or a variable resistance) coupled to the input and output of the inverter series. The method generally includes the steps of applying an operating voltage to such a circuit and generating an oscillator signal. The circuits and methods may be employed as a VCO component of a phase-locked loop. The upper limit of the oscillator signal frequency may be configured by altering or controlling the variable resistance and/or one or more parameters of the LC resonator tank. The circuit design demonstrates a high tolerance to variations in circuit or circuit component values.