The 1/f noise expressions for MOS transistors biased from weak to strong inversion are derived in this paper. The variations of all the factors in the expressions versus the bias voltages are discussed in detail. The theory is in agreement with the experiments. Especially

it can be used to explain the experimental phenomena of strong inversion in the sub-saturation and saturation regions. In addition

the device parameters such as the device capacitance ratio and the threshold voltage can be determined using the present theory. This is a new method which differs from the static characteristic measurement. It is shown that our theory has greater practical value than the others.