Sub-30-mV-Supply, Fully Integrated Ring Oscillator Consisting of Recursive Stacking Body-Bias Inverters for Extremely Low-Voltage Energy Harvesting

This paper presents a ring oscillator (ROSC) consisting of recursive stacking body-bias inverters (RS-BBIs) for low-voltage energy harvesting. The RS-BBI is based on the conventional stacked body-bias inverter and consists of additional inverters stacked at the top and bottom of the inverter recursively. The RS-BBI increases the transconductance of MOSFETs and suppresses the leakage current due to its stacking structure, and increases the on-current of MOSFETs with the body-bias technique. The minimum supply voltage $V_{\mathrm{D}\mathrm{D},\min}$ can be reduced by increasing the number of stacking inverters. Measured results indicate that our ROSCs using the RS-BBIs were able to operate at lower supply voltage as the number of stacking inverters increased. The measured lowest $V_{\mathrm{D}\mathrm{D},\min}$ was 26 mV even though not all chips were able to oscillate. All chips oscillated successfully at 30 mV.