LC oscillators in nanoscale DG-MOSFETs

Abstract

The characteristics of a negative resistance LC oscillator and its quadrature extension have been investigated using nanoscale Double Gate MOSFETs (DG-MOSFET). The oscillatory criterion of g m R ≥ ~ ½ is verified by a small signal analysis for the common mode operation. This is a less stringent oscillatory criterion compared to an equivalent oscillator, designed in conventional CMOS. The observed phase noise in this mode is -133 dBc/Hz at 1 MHz offset. Next the oscillator is operated in the independent mode to vary the oscillation frequency via back gate bias. This unique feature of the DG-MOSFET substitutes the requirement of MOS varactors. A novel quantitative response for the voltage control characteristic of the oscillator has been established which is supported with theory and verified by simulations. The characteristic is dissimilar to the voltage control attribute of a Voltage Control Oscillator in the conventional single gate MOSFET. Finally, the quadrature LC oscillator is designed with only four transistors against eight required in single gate MOSFET architecture. The phase noise, phase error and the coupling strength of the proposed quadrature oscillator are -107 dBc/Hz at 1 MHz offset, 0.6° and 1 respectively. All the design and analyses are implemented in 32 nm DG-MOSFET/DG-FinFET technology.