Efficient logic cell design for ultralow-energy subthreshold operation in wearable biomedical systems

Abstract

This paper explores efficient logic cell design strategies for ultralow-energy subthreshold operation in wearable biomedical systems. Traditional logic cell design approaches often lead to suboptimal efficiency due to unbalanced Pull-Up (PU) and Pull-Down (PD) networks. Various techniques are examined, including balanced PU/PD network design using body biasing and statistical distribution analysis of drain-source current. Moreover, the reverse channel (RSC) effect is investigated for device optimization. Single-stage gates such as inverters, NAND, and NOR gates are designed with Mentor Graphics tools to minimize power dissipation and area. Multistage gates like XOR and XNOR gates are also optimized for reduced signal propagation delay. A detailed analysis of D-flip-flop designs with varying transistor counts is presented. Power dissipation, delay, rise time, and fall time characteristics are compared for flip-flop configurations comprising 18, 10, and 5 transistors. The results indicate significant energy optimization with the proposed designs, particularly with the 5-transistor configuration, demonstrating the effectiveness of the proposed methodologies in achieving superior energy efficiency and reduced signal noise in biomedical systems.