A study of second saturation effect of OPTVLD NMOS

A detail analysis of the mechanism of output characteristic of OPTimized Variation Lateral Doping (OPTVLD) N-type MOS is presented in this paper. While a first current saturation of channel current is caused by the parasitic Junction FET (JFET), a second saturation is found in the state of high level drain current-voltage, which is explained by the enhancement of drain current with the increasing of drain voltage at high gate voltage due to that the carriers introduced by current modulate the electric field and cause intense impact ionization effect. It is expected that the analysis presented here can be used to improve the output characteristic of OPTVLD NMOS.