Positive current is defined to flow into each teminal.
L and W are the channel's length and width. AD and AS are the drain and source diffusion areas. PD and PS are the drain and source diffusion parameters. The zero-bias depletion capacitances can be specified by CJ, which is multiplied by AD and AS, and by CJSW, which is multiplied by PD and PS, or by CBD and CBS, which are absolute values. NRD, NRS, NRG, and NRB are realtive resistivities of their respective terminals in squares.