Low power active load and IMOS varactor based VCO designs using differential delay stages in 0.18 ​μm technology

This paper proposes low power differential voltage-controlled oscillators (VCOs) with active load and IMOS varactor in delay stages. VCO circuits utilize two NOR gates in differential mode. The different levels of gate bias voltage ( V b i a s ) of the PMOS/NMOS active load along with variations in the varactor control voltage ( V c o n t r o l ) of inversion mode MOSFET (IMOS) achieves a wide frequency tuning range. PMOS active load VCO shows the output frequency range from 4.656 ​GHz to 5.333 ​GHz and power dissipation of 2.539 ​mW. NMOS active load VCO shows the output frequency range from 4.782 ​GHz to 5.516 ​GHz and power dissipation of 2.225 ​mW. The results with different width of varactor diode and bias voltages of active load are also reported in this work. Proposed VCO circuits are showing a phase noise of −102.37 dBc/Hz for PMOS active load, and −98.63 dBc/Hz for NMOS active load at 1 ​MHz offset with the corresponding figure of merit (FoM) of −172.86 dBc and −168.41 dBc, respectively.