Dependence of 1/f noise characteristics of NMOSFETs on body bias and temperature in sub-threshold region

Low frequency noise has become one of the major issues for an analog mixed signal and RF (radio frequency) circuits [1]. Previous studies have extensively analyzed drain/gate bias and temperature dependence of 1/f (flicker) noise in a strong inversion region [2, 3], whereas 1/f noise in a sub-threshold region has been investigated very little. The demand for low power consumption has increased due to the development of single battery cell phones. Hence, to reduce the dynamic power consumption of CMOS circuits, threshold voltage must be scaled down without degrading circuit speed or operating logic noise margins. Although V_th scaling is limited by the off-current and static power consumption constraints, a constant substrate biasing technique is used with standard CMOS technology to improve the performance of CMOS circuits. As this technique is used in analog-integrated circuits, such as current mirror and VCO (voltage controlled oscillator), the dependence of 1/f noise characteristics on body bias need to be analyzed. In addition, the noise characteristic of MOSFETs at high temperature is important for analog circuits because the analog circuits are more sensitive to temperature [4, 5]. However, there was little study on the noise characteristics concurrently considering the body bias and temperature. In this study, 1/f noise characteristics of NMOSFET were investigated for various body bias and temperature in a sub-threshold region.