Noise Analysis of the Designed COs

In this section, the noise analyses of the four COs designed and simulated in this work have been done. Noise is defined as the random fluctuations that affect currents and voltages and it actually sets the lower limit of any signal without its quality being deteriorated. For the conventional MOS based CO, noise analysis takes into account the Thermal noise, Shot noise and Flicker noise. Thermal noise, also called as Nyquist or Johnson noise, is associated with the random thermal motion of charge carriers. Shot noise is caused by the random fluctuations of the electric current due to electronic charge and the Flicker noise, also called 1/f noise or pink noise, is present in both the active and passive devices and becomes predominant at lower frequencies. In the Stanford CNTFET model no noise source definition exits. However, in various works noise models have been provided as an extension to the Stanford CNTFET model; providing high flexibility to choose the circuit simulators. In this work, an equivalent small signal analysis model and the parameter extraction principle have been employed for the noise analysis of the CNTFET based COs. The intrinsic and extrinsic parameters have been extracted using s-parameter analysis and then subsequently converted to Y and Z parameters. In CNTFETs, the noise modeling can be done in both the saturation and triode regions [26,30]. The various noise sources included in the analysis include thermal noise, shot channel noise and the flicker noise. Figure 25 shows the equivalent circuit of a CNTFET with added noise sources used in analysis. The total noise is the root mean square value of the individual noise contributions.