Implications of Small Geometry Effects on $g_m/I_D$ Based Design Methodology for Analog Circuits

Small geometry effects have become increasingly important in analog circuits as transistors continue to shrink. As a result, transconductance-to-drain current (g
_m
/I
_D
) transistor parameters are no longer width-independent. In this brief, a procedure to develop “unit-sized” transistors with minimal sensitivity to small geometry effects is proposed. It is shown that by using the unit-sized transistors, the impact of small geometry effects on g
_m
/I
_D
dependent parameters such as current density and self gain can be reduced to 3.6% and 1.5%, respectively.