Optimization of MOS amplifier performance through channel length and inversion level selection

The dependence of MOS amplifier performance on channel length and channel inversion is simulated and discussed. Suggestions are made regarding the optimization of voltage gain, nonlinear distortion and the gain-bandwidth product (GBW) through careful device length and inversion level selection. The midband voltage gain of the common-source amplifier is shown to remain relatively constant when biased for weak inversion operation, with short-channel devices continuing to amplify effectively at very low levels of inversion, allowing for extremely low power circuits. Total harmonic distortion is reduced through decreasing channel length and/or the level of channel inversion. The GBW is optimized through the use of minimum sized transistors biased to operate in the strong inversion region.