IMPROVEMENTS IN LOW-FREQUENCY NOISE OF MOSFETS FOR FRONT END AMPLIFIERS

Studies of physical noise mechanisms in transistors show that a MOSFET in inversion will exhibit a 1 f{hook} noise spectrum proportional to the volumetric trap density in the oxide, inversely proportional to the gate area and independent of bias or temperature over the entire usable range. A depletion mode MOSFET at aroundroom temperature, owing to its 1 f{hook}2 spectrum, will shown an improvement over a limited range of frequencies which is related to the interface state density and the intrinsic carrier density in Si. At reduced temperatures depletion mode MOSFETs can be equal to the best JFETs but devices in CCDs and other similar applications do not yet demonstrate this potential. The noise performance of n and p channel devices in CMOS processes are compared. © 1990.