A one-dimensional DC model for nonrectangular IGFETs

The drain current of a nonrectangular IGFET operating in the triode and subthreshold regions is shown to be identical to that of a rectangular device of an appropriate effective aspect ratio. The effective aspect ratio can be calculated by conformal mapping techniques, or by two-dimensional numerical methods. Experimental results are presented demonstrating the scaling property for a variety of nonrectangular IGFET configurations. The theory developed is then used to derive an equivalent circuit for IGFETs having more than one source or drain. An approximate analysis is performed which results in an expression for the increase in drain current of a bent IGFET in the saturation region.