Ultra low voltage supply VCO with improved linearity

Abstract

In this paper, we present a VCO designed for operation at 250 mV dissipating 590 nW, free running frequency of 462 kHz with voltage-to-frequency maximum non-linearity of 0.33%. The VCO design aim to a time based ADC, whose resolution is highly limited by the non-linearity of the VCO itself, which may be corrected by further digital calibration. The proposed VCO uses a ring oscillator topology and employs forward body biasing to achieve high linearity in the analog domain.