This work presents an Improved Charge Sheet compact Model (ICSM) especially valuable for distortion analysis, where precise calculation of derivatives of at least third order is required. A new expression for the charge is used in the calculation of the current. Vertical electric field, mobility and DIBL are represented using previously reported for other purposes more precise expressions. The very good agreement obtained between experimental PD SOI MOSFETs with channel lengths from 0.32 to 10μm and modeled currents, derivatives and distortion figures is shown.