Low THD ±0.75 V 32 nm CNFET Quadrature VCO for PLL and Costas-Loop Applications

In this paper, first a new Analog Building Block (ABB) viz. the Carbon Nanotube Field Effect Transistor (CNFET)-based voltage-controlled current conveyor (VCCC) is presented. Thereafter, a voltage-mode resistor-less quadrature oscillator is proposed which employs three CNFET-based VCCCs and three capacitors. The proposed Voltage-Controlled Oscillator (VCO) can provide two sinusoidal quadrature voltage outputs. The bias voltage of VCCC can be adjusted to electronically control the frequency of oscillation and condition of oscillation of the Quadrature Voltage-Controlled Oscillator (QVCO). VCOs find applications in Phase-Locked Loops (PLLs) and receivers for amplitude modulation systems. The VCO output can also be used to generate a clock signal for a digital system. Results of HSPICE simulations using 32 nm CNFET parameters at ±0.75 V biasing voltages show good agreement to theoretical assumptions. The THD performance of the proposed quadrature VCO was found to be excellent with the distortion values lying well below 3 % for both the voltage outputs.