Floating-body effects in partially depleted SOI CMOS circuits

This paper presents a detailed study on the impact of a floating body in partially depleted (PD) silicon-on-insulator (SOI) MOSFET´s on various CMOS circuits. Digital very large scale integration (VLSI) CMOS circuit families including static and dynamic CMOS logic, static cascade voltage switch logic (static CVSL), and dynamic cascade voltage switch logic (dynamic CVSL) are investigated with particular emphasis on circuit topologies where the parasitic bipolar effect resulting from the floating body affects the circuit operation and stability. Commonly used circuit building blocks for fast arithmetic operations in processor data-flow, such as static and dynamic carry lookahead circuits and Manchester carry chains, are examined. Pass-transistor-based designs including latch, multiplexer, and pseudo two-phase dynamic logic are then discussed. It is shown that under certain circuit topologies and switching patterns, the parasitic bipolar effect causes extra power consumption and degrades the noise margin and stability of the circuits. In certain dynamic circuits, the parasitic bipolar effect is shown to cause logic state error if not properly accounted for.