In this paper, we identify the level shifter (LS) for voltage up-conversion from the ultralow-voltage regime as a key application domain of tunnel FETs (TFETs). We propose a mixed TFET–MOSFET LS design methodology, which exploits the complementary characteristics of TFET and MOSFET devices. Simulation results show that the hybrid LS exhibits superior dynamic performance at the same static power consumption compared with the conventional MOSFET and pure TFET solutions. The advantage of the mixed design with respect to the conventional MOSFET approach is emphasized when lower voltage signals have to be up-converted, reaching an improvement of the energy-delay product up to three decades. When compared with the full MOSFET design, the mixed TFET–MOSFET solution appears to be less sensitive toward threshold voltage variations in terms of dynamic figures of merit, at the expense of higher leakage variability. Similar results are obtained for four different LS topologies, thus indicating that the hybrid TFET–MOSFET approach offers intrinsic advantages in the design of LS for voltage up-conversion from the ultralow-voltage regime compared with the conventional MOSFET and pure TFET solutions.
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