A key component of VCO-ADCs is the ring oscillator, which determines the circuit and quantization noise of the converter. The input-referred thermal and flicker noise of a VCO-ADC stems from the VCO driver source and the VCO phase noise. On the other hand, quantization noise depends on the oscillation frequency of the VCO with respect to the sampling frequency. An optimal VCO-ADC design should balance oscillation frequency with flicker and thermal contributions of the VCO. In this paper, we show a simple modification of the conventional stages used in VCO-ADC ring oscillators. The modification consists of including two extra transistors in series, isolating the inverter from the power rails when switching. This modification allows one to significantly increase the oscillation frequency while having similar phase noise contributions compared to other ring oscillator architectures with the same area and power.